Sets or gets a value which indicates whether the source column is nullable. This allows DbCommandBuilder to correctly generate Update statements for nullable columns.
Assembly: System.Data (in System.Data.dll)
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 DbCommandBuilder is generating its Update statement, it examines the for each parameter. If the property is true, DbCommandBuilder 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 for the field is false, DbCommandBuilder 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.