Gets or sets the name of the method or function that the ObjectDataSource control invokes to update data.
Assembly: System.Web (in System.Web.dll)
The ObjectDataSource control assumes that the method that is identified by the property performs updates one at a time, rather than in a batch.
The method that is identified by the property can be an instance method or a static (Shared in Visual Basic) method. If it is an instance method, the business object is created and destroyed each time the method that is specified by the property is called. You can handle the ObjectCreated and ObjectCreating events to work with the business object before the method that is specified by the property is called. You can also handle the ObjectDisposing event that is raised after the method that is specified by the property is called. If the business object implements the IDisposable interface, the Dispose method is called before the object is destroyed. If the method is static (Shared in Visual Basic), the business object is never created and you cannot handle the ObjectCreated, ObjectCreating, and ObjectDisposing events.
Parameters are added to the UpdateParameters collection from three sources:
From the data-bound control, at run time.
From the UpdateParameters element, declaratively.
From the Updating event handler, programmatically.
First, any parameters that are generated from data-bound controls are added to the UpdateParameters collection. For example, if the ObjectDataSource control is bound to a GridView control that has the columns Name and Number, the parameters for Name and Number are added to the collection. The exact name of the parameter depends on the OldValuesParameterFormatString property. The data type of these parameters is string. Next, the parameters that are listed in the UpdateParameters element are added. If a parameter in the UpdateParameters element is found with the same name as a parameter that is already in the UpdateParameters collection, the existing parameter is modified to match the parameter that is specified in the UpdateParameters element. Typically, this is used to modify the type of the data in the parameter. Finally, you can programmatically add and remove parameters in the Updating event, which occurs before the Update method is run. The method is resolved after the parameters are merged. Method resolution is discussed in the next section.
You should validate any parameter value that you receive from the client. The runtime simply substitutes the parameter value into the property.
When the Update method is called, the data fields from the data-bound control, the parameters that were created declaratively in the UpdateParameters element, and the parameters that were added in the Updating event handler are all merged. (For more information, see the preceding section.) The ObjectDataSource control then attempts to find a method to call. First, it looks for one or more methods with the name that is specified in the property. If no match is found, an InvalidOperationException exception is thrown. If a match is found, it then looks for matching parameter names. For example, suppose a type that is specified by the TypeName property has two methods named UpdateARecord. One UpdateARecord has one parameter, ID, and the other UpdateARecord has two parameters, Name and Number. If the UpdateParameters collection has only one parameter named ID, the UpdateARecord method with just the ID parameter is called. The type of the parameter is not checked in resolving the methods. The order of the parameters does not matter.
If the DataObjectTypeName property is set, the method is resolved in a different way. The ObjectDataSource looks for a method with the name that is specified in the property that takes one parameter of the type that is specified in the DataObjectTypeName property. In this case, the name of the parameter does not matter.
The following three examples show a Web page, a code-behind page class, and a data-access class that enable a user to retrieve and update records in the Employees table in the Northwind database.
The first example shows a Web page that contains two ObjectDataSource controls, a DropDownList control, and a DetailsView control. The first ObjectDataSource control and the DropDownList control are used to retrieve and display employee names from the database. The second ObjectDataSource control and the DetailsView control are used to retrieve, display, and modify the data from the employee record that is selected by the user.
<form id="form1" runat="server"> <asp:objectdatasource ID="ObjectDataSource1" runat="server" SelectMethod="GetFullNamesAndIDs" TypeName="Samples.AspNet.CS.EmployeeLogic" /> <p> <asp:dropdownlist ID="DropDownList1" runat="server" DataSourceID="ObjectDataSource1" DataTextField="FullName" DataValueField="EmployeeID" AutoPostBack="True" AppendDataBoundItems="true"> <asp:ListItem Text="Select One" Value=""></asp:ListItem> </asp:dropdownlist> </p> <asp:objectdatasource ID="ObjectDataSource2" runat="server" SelectMethod="GetEmployee" UpdateMethod="UpdateEmployeeAddress" OnUpdating="EmployeeUpdating" OnSelected="EmployeeSelected" TypeName="Samples.AspNet.CS.EmployeeLogic" > <SelectParameters> <asp:ControlParameter ControlID="DropDownList1" DefaultValue="-1" Name="empID" /> </SelectParameters> </asp:objectdatasource> <asp:DetailsView ID="DetailsView1" runat="server" DataSourceID="ObjectDataSource2" AutoGenerateRows="false" AutoGenerateEditButton="true"> <Fields> <asp:BoundField HeaderText="Address" DataField="Address" /> <asp:BoundField HeaderText="City" DataField="City" /> <asp:BoundField HeaderText="Postal Code" DataField="PostalCode" /> </Fields> </asp:DetailsView> </form>
The second example shows handlers for the Selected and Updating events. The Selected event handler serializes the object that contains data that was retrieved from the Employee table. The serialized object is stored in view state. The Updating event handler deserializes the object in view state that contains the original data for the data record that is being updated. The object that contains the original data is passed as a parameter to the Update method. The original data must be passed to the database so that it can be used to check whether the data has been modified by another process.
Public Sub EmployeeUpdating(ByVal source As Object, ByVal e As ObjectDataSourceMethodEventArgs) Dim dcs As New DataContractSerializer(GetType(Employee)) Dim xmlData As String Dim reader As XmlReader Dim originalEmployee As Employee xmlData = ViewState("OriginalEmployee").ToString() reader = XmlReader.Create(New StringReader(xmlData)) originalEmployee = CType(dcs.ReadObject(reader), Employee) reader.Close() e.InputParameters.Add("originalEmployee", originalEmployee) End Sub Public Sub EmployeeSelected(ByVal source As Object, ByVal e As ObjectDataSourceStatusEventArgs) If e.ReturnValue IsNot Nothing Then Dim dcs As New DataContractSerializer(GetType(Employee)) Dim sb As New StringBuilder() Dim writer As XmlWriter writer = XmlWriter.Create(sb) dcs.WriteObject(writer, e.ReturnValue) writer.Close() ViewState("OriginalEmployee") = sb.ToString() End If End Sub
The third example shows the data access class that interacts with the Northwind database. The class uses LINQ to query and update the Employees table. The example requires a LINQ to SQL class that represents the Northwind database and Employees table. For more information, see How to: Create LINQ to SQL Classes in a Web Project.
Public Class EmployeeLogic Public Shared Function GetFullNamesAndIDs() As Array Dim ndc As New NorthwindDataContext() Dim employeeQuery = _ From e In ndc.Employees _ Order By e.LastName _ Select FullName = e.FirstName + " " + e.LastName, EmployeeID = e.EmployeeID Return employeeQuery.ToArray() End Function Public Shared Function GetEmployee(ByVal empID As Integer) As Employee If (empID < 0) Then Return Nothing Else Dim ndc As New NorthwindDataContext() Dim employeeQuery = _ From e In ndc.Employees _ Where e.EmployeeID = empID _ Select e Return employeeQuery.Single() End If End Function Public Shared Sub UpdateEmployeeAddress(ByVal originalEmployee As Employee, ByVal address As String, ByVal city As String, ByVal postalcode As String) Dim ndc As New NorthwindDataContext() ndc.Employees.Attach(originalEmployee, False) originalEmployee.Address = address originalEmployee.City = city originalEmployee.PostalCode = postalcode ndc.SubmitChanges() End Sub End Class