.NET Framework 4 Creating a DataTable From a Query (LINQ to DataSet) Data binding is a common use of DataTable object. The CopyToDataTable method takes the results of a query and copies the data into a DataTable, which can then be used for data binding. When the data operations have been performed, the new DataTable is merged back into the source DataTable. The CopyToDataTable method uses the following process to create a DataTable from a query: The CopyToDataTable method clones a DataTable from the source table (a DataTable object that implements the IQueryable<(Of <(T>)>) interface). The IEnumerable source has generally originated from a LINQ to DataSet expression or method query. The schema of the cloned DataTable is built from the columns of the first enumerated DataRow object in the source table and the name of the cloned table is the name of the source table with the word "query" appended to it. For each row in the source table, the content of the row is copied into a new DataRow object, which is then inserted into the cloned table. The RowState and RowError properties are preserved across the copy operation. An ArgumentException is thrown if the DataRow objects in the source are from different tables. The cloned DataTable is returned after all DataRow objects in the input queryable table have been copied. If the source sequence does not contain any DataRow objects, the method returns an empty DataTable.
Note that calling the CopyToDataTable method will cause the query bound to the source table to execute. When the CopyToDataTable method encounters either a null reference or nullable value type in a row in the source table, it replaces the value with Value. This way, null values are handled correctly in the returned DataTable. Note: The CopyToDataTable method accepts as input a query that can return rows from multiple DataTable or DataSet objects. The CopyToDataTable method will copy the data but not the properties from the source DataTable or DataSet objects to the returned DataTable. You will need to explicitly set the properties on the returned DataTable, such as Locale and TableName. The following example queries the SalesOrderHeader table for orders after August 8, 2001 and uses the CopyToDataTable method to create a DataTable from that query. The DataTable is then bound to a BindingSource, which acts as proxy for a DataGridView.
' Bind the System.Windows.Forms.DataGridView object
' to the System.Windows.Forms.BindingSource object.
dataGridView.DataSource = bindingSource
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
' Query the SalesOrderHeader table for orders placed
' after August 8, 2001.
Dim query = _
From order In orders.AsEnumerable() _
Where order.Field(Of DateTime)("OrderDate") > New DateTime(2001, 8, 1) _
Select order
' Create a table from the query.
Dim boundTable As DataTable = query.CopyToDataTable()
' Bind the table to a System.Windows.Forms.BindingSource object,
' which acts as a proxy for a System.Windows.Forms.DataGridView object.
bindingSource.DataSource = boundTable
// Bind the System.Windows.Forms.DataGridView object
// to the System.Windows.Forms.BindingSource object.
dataGridView.DataSource = bindingSource;
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
// Query the SalesOrderHeader table for orders placed
// after August 8, 2001.
IEnumerable<DataRow> query =
from order in orders.AsEnumerable()
where order.Field<DateTime>("OrderDate") > new DateTime(2001, 8, 1)
select order;
// Create a table from the query.
DataTable boundTable = query.CopyToDataTable<DataRow>();
// Bind the table to a System.Windows.Forms.BindingSource object,
// which acts as a proxy for a System.Windows.Forms.DataGridView object.
bindingSource.DataSource = boundTable;
Creating a Custom CopyToDataTable Method
The existing CopyToDataTable methods only operate on an IEnumerable<(Of <(T>)>) source where the generic parameter T is of type DataRow. Although this is useful, it does not allow tables to be created from a sequence of scalar types, from queries that return anonymous types, or from queries that perform table joins. For an example of how to implement two custom CopyToDataTable methods that load a table from a sequence of scalar or anonymous types, see How to: Implement CopyToDataTable<T> Where the Generic Type T Is Not a DataRows. The examples in this section use the following custom types:
Public Class Item
Private _Id As Int32
Private _Price As Double
Private _Genre As String
Public Property Id() As Int32
Get
Return Id
End Get
Set(ByVal value As Int32)
_Id = value
End Set
End Property
Public Property Price() As Double
Get
Return _Price
End Get
Set(ByVal value As Double)
_Price = value
End Set
End Property
Public Property Genre() As String
Get
Return _Genre
End Get
Set(ByVal value As String)
_Genre = value
End Set
End Property
End Class
Public Class Book
Inherits Item
Private _Author As String
Public Property Author() As String
Get
Return _Author
End Get
Set(ByVal value As String)
_Author = value
End Set
End Property
End Class
Public Class Movie
Inherits Item
Private _Director As String
Public Property Director() As String
Get
Return _Director
End Get
Set(ByVal value As String)
_Director = value
End Set
End Property
End Class
public class Item
{
public int Id { get; set; }
public double Price { get; set; }
public string Genre { get; set; }
}
public class Book : Item
{
public string Author { get; set; }
}
public class Movie : Item
{
public string Director { get; set; }
}
ExampleThis example performs a join over the SalesOrderHeader and SalesOrderDetail tables to get online orders from the month of August and creates a table from the query.
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
Dim details As DataTable = ds.Tables("SalesOrderDetail")
Dim query = _
From order In orders.AsEnumerable() _
Join detail In details.AsEnumerable() _
On order.Field(Of Integer)("SalesOrderID") Equals _
detail.Field(Of Integer)("SalesOrderID") _
Where order.Field(Of Boolean)("OnlineOrderFlag") = True And _
order.Field(Of DateTime)("OrderDate").Month = 8 _
Select New With _
{ _
.SalesOrderID = order.Field(Of Integer)("SalesOrderID"), _
.SalesOrderDetailID = detail.Field(Of Integer)("SalesOrderDetailID"), _
.OrderDate = order.Field(Of DateTime)("OrderDate"), _
.ProductID = detail.Field(Of Integer)("ProductID") _
}
Dim table As DataTable = query.CopyToDataTable()
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
DataTable details = ds.Tables["SalesOrderDetail"];
var query =
from order in orders.AsEnumerable()
join detail in details.AsEnumerable()
on order.Field<int>("SalesOrderID") equals
detail.Field<int>("SalesOrderID")
where order.Field<bool>("OnlineOrderFlag") == true
&& order.Field<DateTime>("OrderDate").Month == 8
select new
{
SalesOrderID =
order.Field<int>("SalesOrderID"),
SalesOrderDetailID =
detail.Field<int>("SalesOrderDetailID"),
OrderDate =
order.Field<DateTime>("OrderDate"),
ProductID =
detail.Field<int>("ProductID")
};
DataTable orderTable = query.CopyToDataTable();
ExampleThe following example queries a collection for items of price greater than $9.99 and creates a table from the query results.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Query for items with price greater than 9.99.
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
Dim table As DataTable
table = query.CopyToDataTable()
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Query for items with price greater than 9.99.
var query = from i in items
where i.Price > 9.99
orderby i.Price
select i;
// Load the query results into new DataTable.
DataTable table = query.CopyToDataTable();
ExampleThe following example queries a collection for items of price greater than 9.99 and projects the results. The returned sequence of anonymous types is loaded into an existing table.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Create a table with a schema that matches that of the query results.
Dim table As DataTable = New DataTable()
table.Columns.Add("Price", GetType(Integer))
table.Columns.Add("Genre", GetType(String))
' Query for items with price greater than 9.99.
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
query.CopyToDataTable(table, LoadOption.PreserveChanges)
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Create a table with a schema that matches that of the query results.
DataTable table = new DataTable();
table.Columns.Add("Price", typeof(int));
table.Columns.Add("Genre", typeof(string));
var query = from i in items
where i.Price > 9.99
orderby i.Price
select new { i.Price, i.Genre };
query.CopyToDataTable(table, LoadOption.PreserveChanges);
ExampleThe following example queries a collection for items of price greater than $9.99 and projects the results. The returned sequence of anonymous types is loaded into an existing table. The table schema is automatically expanded because the Book and Movies types are derived from the Item type.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Load into an existing DataTable, expand the schema and
' autogenerate a new Id.
Dim table As DataTable = New DataTable()
Dim dc As DataColumn = table.Columns.Add("NewId", GetType(Integer))
dc.AutoIncrement = True
table.Columns.Add("ExtraColumn", GetType(String))
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
query.CopyToDataTable(table, LoadOption.PreserveChanges)
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Load into an existing DataTable, expand the schema and
// autogenerate a new Id.
DataTable table = new DataTable();
DataColumn dc = table.Columns.Add("NewId", typeof(int));
dc.AutoIncrement = true;
table.Columns.Add("ExtraColumn", typeof(string));
var query = from i in items
where i.Price > 9.99
orderby i.Price
select new { i.Price, i.Genre };
query.CopyToDataTable(table, LoadOption.PreserveChanges);
ExampleThe following example queries a collection for items of price greater than $9.99 and returns a sequence of Double, which is loaded into a new table.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select i.Price
Dim table As DataTable
table = query.CopyToDataTable()
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// load sequence of scalars.
IEnumerable<double> query = from i in items
where i.Price > 9.99
orderby i.Price
select i.Price;
DataTable table = query.CopyToDataTable();
See Also
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.NET Framework 4 Crear DataTable desde una consulta (LINQ to DataSet) El enlace de datos es una utilización muy frecuente del objeto DataTable. El método CopyToDataTable toma los resultados de una consulta y copia los datos en un objeto DataTable que puede utilizarse después para el enlace de datos. Cuando las operaciones de datos se han realizado, el DataTable nuevo se vuelve a combinar en el DataTable de origen. El método CopyToDataTable utiliza el siguiente proceso para crear un DataTable a partir de una consulta: El método CopyToDataTable clona un DataTable a partir de la tabla origen (un objeto DataTable que implementa la interfaz IQueryable<(Of <(T>)>)). El origen de IEnumerable se ha originado de una expresión LINQ to DataSet o una consulta de método. El esquema del DataTable clonado se compila a partir de las columnas del primer objeto DataRow enumerado en la tabla origen; el nombre de la tabla clonada es el nombre de la tabla origen con la palabra "query" anexada. En cada fila de la tabla origen, el contenido de la fila se copia en un objetoDataRow nuevo, el cual, a continuación, se inserta en la tabla clonada. Las propiedades RowState y RowError se mantienen en toda la operación de copia. Si los objetos DataRow de origen pertenecen a tablas diferentes, se produce unaArgumentException. Cuando todos los objetos DataRow de la tabla de entrada que se puede consultar se han copiado, se devuelve el DataTable clonado. Si la secuencia origen no contiene objetos DataRow, el método devuelve un DataTable vacío.
Observe que, si se llama al método CopyToDataTable, la consulta se enlaza a la tabla origen para ejecutarse. Cuando el método CopyToDataTable encuentra una referencia NULL o un tipo de valor que admite valores NULL en una fila de la tabla origen, reemplaza el valor con Value. De este modo, los valores NULL se controlan correctamente en el DataTable devuelto. Nota: el método CopyToDataTable acepta como entrada una consulta que pueda devolver filas de varios objetos DataTable o DataSet. El método CopyToDataTable copiará los datos pero no las propiedades desde los objetos DataTable o DataSet de origen en el elemento DataTable que se va a devolver. Necesitará establecer explícitamente las propiedades de los elementos DataTable devueltos, como Locale y TableName. En el ejemplo siguiente se consultan en la tabla SalesOrderHeader los pedidos posteriores al 8 de agosto de 2001 y se utiliza el método CopyToDataTable para crear un DataTable a partir de esa consulta. A continuación, se enlaza DataTable a un BindingSource, que actúa como proxy para un objeto DataGridView.
' Bind the System.Windows.Forms.DataGridView object
' to the System.Windows.Forms.BindingSource object.
dataGridView.DataSource = bindingSource
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
' Query the SalesOrderHeader table for orders placed
' after August 8, 2001.
Dim query = _
From order In orders.AsEnumerable() _
Where order.Field(Of DateTime)("OrderDate") > New DateTime(2001, 8, 1) _
Select order
' Create a table from the query.
Dim boundTable As DataTable = query.CopyToDataTable()
' Bind the table to a System.Windows.Forms.BindingSource object,
' which acts as a proxy for a System.Windows.Forms.DataGridView object.
bindingSource.DataSource = boundTable
// Bind the System.Windows.Forms.DataGridView object
// to the System.Windows.Forms.BindingSource object.
dataGridView.DataSource = bindingSource;
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
// Query the SalesOrderHeader table for orders placed
// after August 8, 2001.
IEnumerable<DataRow> query =
from order in orders.AsEnumerable()
where order.Field<DateTime>("OrderDate") > new DateTime(2001, 8, 1)
select order;
// Create a table from the query.
DataTable boundTable = query.CopyToDataTable<DataRow>();
// Bind the table to a System.Windows.Forms.BindingSource object,
// which acts as a proxy for a System.Windows.Forms.DataGridView object.
bindingSource.DataSource = boundTable;
Crear un método CopyToDataTable personalizado
Los métodos CopyToDataTable existentes solo funcionan en un origen IEnumerable<(Of <(T>)>) en el que el parámetro genérico T es de tipo DataRow. Aunque esto es útil, no permite la creación de tablas a partir de una secuencia de tipos escalares, a partir de consultas que devuelven tipos anónimos, o a partir de consultas que realizan combinaciones de tablas. Para obtener un ejemplo de cómo se implementan dos métodos CopyToDataTable personalizados que cargan una tabla a partir de una secuencia de tipos anónimos o escalares, vea Cómo implementar CopyToDataTable<T> donde el tipo genérico T no es un objeto DataRow. Los ejemplos de esta sección utilizan los tipos personalizados siguientes:
Public Class Item
Private _Id As Int32
Private _Price As Double
Private _Genre As String
Public Property Id() As Int32
Get
Return Id
End Get
Set(ByVal value As Int32)
_Id = value
End Set
End Property
Public Property Price() As Double
Get
Return _Price
End Get
Set(ByVal value As Double)
_Price = value
End Set
End Property
Public Property Genre() As String
Get
Return _Genre
End Get
Set(ByVal value As String)
_Genre = value
End Set
End Property
End Class
Public Class Book
Inherits Item
Private _Author As String
Public Property Author() As String
Get
Return _Author
End Get
Set(ByVal value As String)
_Author = value
End Set
End Property
End Class
Public Class Movie
Inherits Item
Private _Director As String
Public Property Director() As String
Get
Return _Director
End Get
Set(ByVal value As String)
_Director = value
End Set
End Property
End Class
public class Item
{
public int Id { get; set; }
public double Price { get; set; }
public string Genre { get; set; }
}
public class Book : Item
{
public string Author { get; set; }
}
public class Movie : Item
{
public string Director { get; set; }
}
EjemploEn este ejemplo se realiza una combinación en las tablas SalesOrderHeader y SalesOrderDetail para obtener pedidos en línea del mes de agosto y se crea una tabla a partir de la consulta.
' Fill the DataSet.
Dim ds As New DataSet()
ds.Locale = CultureInfo.InvariantCulture
' See the FillDataSet method in the Loading Data Into a DataSet topic.
FillDataSet(ds)
Dim orders As DataTable = ds.Tables("SalesOrderHeader")
Dim details As DataTable = ds.Tables("SalesOrderDetail")
Dim query = _
From order In orders.AsEnumerable() _
Join detail In details.AsEnumerable() _
On order.Field(Of Integer)("SalesOrderID") Equals _
detail.Field(Of Integer)("SalesOrderID") _
Where order.Field(Of Boolean)("OnlineOrderFlag") = True And _
order.Field(Of DateTime)("OrderDate").Month = 8 _
Select New With _
{ _
.SalesOrderID = order.Field(Of Integer)("SalesOrderID"), _
.SalesOrderDetailID = detail.Field(Of Integer)("SalesOrderDetailID"), _
.OrderDate = order.Field(Of DateTime)("OrderDate"), _
.ProductID = detail.Field(Of Integer)("ProductID") _
}
Dim table As DataTable = query.CopyToDataTable()
// Fill the DataSet.
DataSet ds = new DataSet();
ds.Locale = CultureInfo.InvariantCulture;
FillDataSet(ds);
DataTable orders = ds.Tables["SalesOrderHeader"];
DataTable details = ds.Tables["SalesOrderDetail"];
var query =
from order in orders.AsEnumerable()
join detail in details.AsEnumerable()
on order.Field<int>("SalesOrderID") equals
detail.Field<int>("SalesOrderID")
where order.Field<bool>("OnlineOrderFlag") == true
&& order.Field<DateTime>("OrderDate").Month == 8
select new
{
SalesOrderID =
order.Field<int>("SalesOrderID"),
SalesOrderDetailID =
detail.Field<int>("SalesOrderDetailID"),
OrderDate =
order.Field<DateTime>("OrderDate"),
ProductID =
detail.Field<int>("ProductID")
};
DataTable orderTable = query.CopyToDataTable();
EjemploEn el ejemplo siguiente se consulta una colección de elementos cuyo precio es superior a $ 9,99 y se crea una tabla a partir de los resultados de la consulta.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Query for items with price greater than 9.99.
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
Dim table As DataTable
table = query.CopyToDataTable()
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Query for items with price greater than 9.99.
var query = from i in items
where i.Price > 9.99
orderby i.Price
select i;
// Load the query results into new DataTable.
DataTable table = query.CopyToDataTable();
EjemploEn el ejemplo siguiente se consulta una colección de elementos cuyo precio es superior a $ 9,99 y se proyectan los resultados. La secuencia de tipos anónimos devuelta se carga en una tabla existente.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Create a table with a schema that matches that of the query results.
Dim table As DataTable = New DataTable()
table.Columns.Add("Price", GetType(Integer))
table.Columns.Add("Genre", GetType(String))
' Query for items with price greater than 9.99.
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
query.CopyToDataTable(table, LoadOption.PreserveChanges)
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Create a table with a schema that matches that of the query results.
DataTable table = new DataTable();
table.Columns.Add("Price", typeof(int));
table.Columns.Add("Genre", typeof(string));
var query = from i in items
where i.Price > 9.99
orderby i.Price
select new { i.Price, i.Genre };
query.CopyToDataTable(table, LoadOption.PreserveChanges);
EjemploEn el ejemplo siguiente se consulta una colección de elementos cuyo precio es superior a $ 9,99 y se proyectan los resultados. La secuencia de tipos anónimos devuelta se carga en una tabla existente. El esquema de la tabla se amplía automáticamente porque los tipos Book y Movies se derivan del tipo Item.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
' Load into an existing DataTable, expand the schema and
' autogenerate a new Id.
Dim table As DataTable = New DataTable()
Dim dc As DataColumn = table.Columns.Add("NewId", GetType(Integer))
dc.AutoIncrement = True
table.Columns.Add("ExtraColumn", GetType(String))
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select New With {i.Price, i.Genre}
query.CopyToDataTable(table, LoadOption.PreserveChanges)
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// Load into an existing DataTable, expand the schema and
// autogenerate a new Id.
DataTable table = new DataTable();
DataColumn dc = table.Columns.Add("NewId", typeof(int));
dc.AutoIncrement = true;
table.Columns.Add("ExtraColumn", typeof(string));
var query = from i in items
where i.Price > 9.99
orderby i.Price
select new { i.Price, i.Genre };
query.CopyToDataTable(table, LoadOption.PreserveChanges);
EjemploEn el ejemplo siguiente se consulta una colección de elementos cuyo precio es superior a $ 9,99 y se devuelve una secuencia de Double, que se carga en una tabla nueva.
Dim book1 As New Book()
book1.Id = 1
book1.Price = 13.5
book1.Genre = "Comedy"
book1.Author = "Gustavo Achong"
Dim book2 As New Book
book2.Id = 2
book2.Price = 8.5
book2.Genre = "Drama"
book2.Author = "Jessie Zeng"
Dim movie1 As New Movie
movie1.Id = 1
movie1.Price = 22.99
movie1.Genre = "Comedy"
movie1.Director = "Marissa Barnes"
Dim movie2 As New Movie
movie2.Id = 1
movie2.Price = 13.4
movie2.Genre = "Action"
movie2.Director = "Emmanuel Fernandez"
Dim items(3) As Item
items(0) = book1
items(1) = book2
items(2) = movie1
items(3) = movie2
Dim query = From i In items _
Where i.Price > 9.99 _
Order By i.Price _
Select i.Price
Dim table As DataTable
table = query.CopyToDataTable()
// Create a sequence.
Item[] items = new Item[]
{ new Book{Id = 1, Price = 13.50, Genre = "Comedy", Author = "Gustavo Achong"},
new Book{Id = 2, Price = 8.50, Genre = "Drama", Author = "Jessie Zeng"},
new Movie{Id = 1, Price = 22.99, Genre = "Comedy", Director = "Marissa Barnes"},
new Movie{Id = 1, Price = 13.40, Genre = "Action", Director = "Emmanuel Fernandez"}};
// load sequence of scalars.
IEnumerable<double> query = from i in items
where i.Price > 9.99
orderby i.Price
select i.Price;
DataTable table = query.CopyToDataTable();
Vea también
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