OracleParameter.SourceColumnNullMapping Property
Definition
Important
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Gets or sets a value which indicates whether the source column is nullable. This allows OracleCommandBuilder to correctly generate Update statements for nullable columns.
public:
virtual property bool SourceColumnNullMapping { bool get(); void set(bool value); };public override bool SourceColumnNullMapping { get; set; }member this.SourceColumnNullMapping : bool with get, setPublic Overrides Property SourceColumnNullMapping As BooleanProperty Value
true if the source column is nullable; otherwise, false.
Remarks
SourceColumnNullMapping is used by the OracleCommandBuilder to correctly generate update commands when dealing with nullable columns. Generally, use of SourceColumnNullMapping is limited to developers inheriting from OracleCommandBuilder.
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 OracleCommandBuilder is generating its Update statement, it examines the SourceColumnNullMapping for each parameter. If the property is true, OracleCommandBuilder 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, OracleCommandBuilder 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 Oracle Server, and provides for common code that works across multiple providers.
