默认等效于DBNull.Value

Question

I am trying to pass default to SQL Server in c#.

This code passes null. Is there any way to pass default?

foreach (SqlParameter Parameter in command.Parameters)
{
    if (Convert.ToString(Parameter.Value) == "")
    {
        Parameter.Value = DBNull.Value;
    }
}

Answer 1

Either don't add the parameter, or add the parameter but set the value to null ( not DBNull.Value ). Both have the same effect: the parameter is not passed, therefore the default is used.

Answer 2

You can set the parameter default in SQL-Server (Stored Procedure...)

(@parm varchar(5) = null)
AS
Begin...

And then don't pass the parameter from C# at all.

Answer 3

Here is another solution of sorts -- it appears to search the stored procedure for parameter default values (literally, a pattern search for the assignment in the declaration of the variable), and return any default values that are found. So...you could call this procedure from your c# app to get all of your default values, assign them to local C# vars, and then use them when you call your other procedure.

http://www.codeproject.com/Articles/12939/Figure-Out-the-Default-Values-of-Stored-Procedure

And here is how you could find the default value on a table itself: (you might need to strip the parenthesis off the returned value)

SELECT COLUMN_DEFAULT, replace(replace(COLUMN_DEFAULT,'(',''),')','') as DefaultWithNoParenthesis
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'WHATEVER'

Good luck!