Export (0) Print
Expand All

DataTableReader.IsDBNull Method

Gets a value that indicates whether the column contains non-existent or missing values.

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

'Declaration
Public Overrides Function IsDBNull ( _
	ordinal As Integer _
) As Boolean

Parameters

ordinal
Type: System.Int32

The zero-based column ordinal

Return Value

Type: System.Boolean
true if the specified column value is equivalent to DBNull; otherwise, false.

Implements

IDataRecord.IsDBNull(Int32)

ExceptionCondition
ArgumentOutOfRangeException

The index passed was outside the range of 0 to FieldCount - 1.

DeletedRowInaccessibleException

An attempt was made to retrieve data from a deleted row.

InvalidOperationException

An attempt was made to read or access a column in a closed DataTableReader .

Call this method to see if there are null column values before calling the typed get methods (for example, GetByte, GetChar, and so on) to avoid raising an error.

The following example displays the contents of the column numbered 2 within the passed-in DataTableReader. If the value the column within a particular row is null, the code displays the text <NULL>. If the data within the column of the correct type, the example displays an error message for each row.

Private Sub PrintColumn(ByVal reader As DataTableReader)
   ' Loop through all the rows in the DataTableReader 
   While reader.Read()
      If reader.IsDBNull(2) Then
         Console.Write("<NULL>")
      Else 
         Try
            Console.Write(reader.GetString(2))
         Catch ex As InvalidCastException
            Console.Write("Invalid data type.")
         End Try 
      End If
      Console.WriteLine()
   End While 
End Sub

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Show:
© 2014 Microsoft