How to return SP error message in page itself

In your SP set the output parameter to the error message in catch block. If any error occur. Set the error to output parameter. Otherwise return 0. Try this:
Stored Procedure:

SELECT @Insert_error = ERROR_MESSAGE()
SELECT @Update_error = ERROR_MESSAGE()

Now check the output parameter in front-end and show that.

string retunvalue = (string)sqlcomm.Parameters["@Insert_error"].Value;
if(retunvalue == 0)
{
     //success
}
else
{
    //Show the error message which is there in your retunvalue variable 
}

Although, as I think, you don't need to do these all stuffs. Just handle SqlException and you'll get all your errors. Refer SqlException Class[^].


--Amit