Represents the sole instance of the DBNull class.
Assembly: mscorlib (in mscorlib.dll)
DBNull is a singleton class, which means only this instance of this class can exist.
If a database field has missing data, you can use the property to explicitly assign a DBNull object value to the field. However, most data providers do this automatically.
To evaluate database fields to determine whether their values are DBNull, you can pass the field value to the DBNull.Value.Equals method. However, this method is rarely used because there are a number of other ways to evaluate a database field for missing data. These include the Visual Basic IsDBNull function, the Convert::IsDBNull method, the DataTableReader::IsDBNull method, the IDataRecord::IsDBNull method, and several other methods.
The following example calls the DBNull.Value.Equals method to determine whether a database field in a contacts database has a valid value. If it does, the field value is appended to the string output in a label.