sql server - How can I deal with the return of a null value parameter from a stored procedure to C# code? -

i have application gets grade name , pass parameter stored procedure. works except case there no grade name in grade table. need modify parameters make them accept null and/or need modify place assign parameters c# parameters can make accept value or null?

i have stored procedure. it's been shortened question:

create procedure sp_mark_test     @gradename    nvarchar(10) output,     @gradepass    bit output begin    -- example only, real code not hard code in 99    select top 1 @gradename = grade.name, @gradepass = grade.pass                        admintest                       testid = 99  end 

here c# code:

var sql = @"dbo.sp_mark_test @gradename out,                              @gradepass out"; sqlparameter[] parameters = new sqlparameter[] {                 new sqlparameter("@gradename", sqldbtype.nvarchar) { direction = parameterdirection.output,size = 10 },    new sqlparameter("@gradepass", sqldbtype.bit) { direction = parameterdirection.output }             };  await db.database.executesqlcommandasync(sql, parameters); var gradename = (string)parameters[1].value; var gradepass = (boolean)parameters[2].value; 

as requested, , quick answer, use of dbnull such as

cmd.parameters.addwithvalue("@closedate", dbnull.value); 

or use comparisons.

msdn page on dbnull class. code snippet below:

if (! dbnull.value.equals(row[fieldname]))      return (string) row[fieldname] + " ";     else     return string.empty;