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SourceColumnNullMapping Property

SqlParameter.SourceColumnNullMapping Property

Note: This property is new in the .NET Framework version 2.0.

Sets or gets a value which indicates whether the source column is nullable. This allows SqlCommandBuilder to correctly generate Update statements for nullable columns.

Namespace: System.Data.SqlClient
Assembly: System.Data (in system.data.dll)

public override bool SourceColumnNullMapping { get; set; 
/** @property */
public boolean get_SourceColumnNullMapping ()

/** @property */
public void set_SourceColumnNullMapping (boolean value)

public override function get SourceColumnNullMapping () : boolean

public override function set SourceColumnNullMapping (value : boolean)

Property Value

true if the source column is nullable; false if it is not.

SourceColumnNullMapping is used by the SqlCommandBuilder to correctly generate update commands when dealing with nullable columns. Generally, use of SourceColumnNullMapping is limited to developers inheriting from SqlCommandBuilder.

DbCommandBuilder uses this property to determine whether the source column is nullable, and sets this property to true if it is nullable, and false if it is not. When SqlCommandBuilder is generating its Update statement, it examines the SourceColumnNullMapping for each parameter. If the property is true, SqlCommandBuilder generates a WHERE clauses like the following (in this query expression, "FieldName" represents the name of the field):

((@IsNull_FieldName = 1 AND FieldName IS NULL) OR 
  (FieldName = @Original_FieldName))

If SourceColumnNullMapping for the field is false, SqlCommandBuilder generates the following WHERE clause:

FieldName = @OriginalFieldName

In addition, @IsNull_FieldName contains 1 if the source field contains null, and 0 if it does not. This mechanism allows for a performance optimization in SQL Server, and provides for common code that works across multiple providers.

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0

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