INullable.IsNull Property


Indicates whether a structure is null. This property is read-only.

Namespace:   System.Data.SqlTypes
Assembly:  System.Data (in System.Data.dll)

bool IsNull { get; }

Property Value

Type: System.Boolean

SqlBooleantrue if the value of this object is null. Otherwise, false.

The default value for any System.Data.SqlTypes instance is null. Use IsNull property to test for null values.

The following code example creates a DataTable with two columns defined as SqlInt32 and SqlString. The code adds one row of known values, one row of null values and then iterates through the DataTable, assigning the values to variables and displaying the output in the console window.

static private void WorkWithSqlNulls()
    DataTable table = new DataTable();

    // Specify the SqlType for each column.
    DataColumn idColumn =
        table.Columns.Add("ID", typeof(SqlInt32));
    DataColumn descColumn =
        table.Columns.Add("Description", typeof(SqlString));

    // Add some data.
    DataRow nRow = table.NewRow();
    nRow["ID"] = 123;
    nRow["Description"] = "Side Mirror";

    // Add null values.
    nRow = table.NewRow();
    nRow["ID"] = SqlInt32.Null;
    nRow["Description"] = SqlString.Null;

    // Initialize variables to use when
    // extracting the data.
    SqlBoolean isColumnNull = false;
    SqlInt32 idValue = SqlInt32.Zero;
    SqlString descriptionValue = SqlString.Null;

    // Iterate through the DataTable and display the values.
    foreach (DataRow row in table.Rows)
        // Assign values to variables. Note that you 
        // do not have to test for null values.
        idValue = (SqlInt32)row["ID"];
        descriptionValue = (SqlString)row["Description"];

        // Test for null value in ID column.
        isColumnNull = idValue.IsNull;

        // Display variable values in console window.
        Console.Write("isColumnNull={0}, ID={1}, Description={2}",
            isColumnNull, idValue, descriptionValue);

This example displays the following results:

isColumnNull=False, ID=123, Description=Side Mirror
isColumnNull=True, ID=Null, Description=Null

.NET Framework
Available since 1.1
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