如何获得C＃中存储过程的结果？

Question

Here is my code in C#:

float r_discountValue = 0;

SqlConnection con = Constant.GetConnection();

SqlCommand cmd = new SqlCommand("Coupon_GetDiscountFromValidCouponCode", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("@PKCouponCode", SqlDbType.VarChar);
cmd.Parameters["@PKCouponCode"].Value = "DIS_77";

try
{
    con.Open();

    SqlDataReader reader = cmd.ExecuteReader();

    if(reader.Read()){
       r_discountValue = float.Parse(reader[0].ToString());
    }

    reader.Close();
}
catch(Exception exception)
{
    throw exception;
}
finally{
    con.Close();
}

return r_discountValue;

The stored procedure:

ALTER PROCEDURE [dbo].[Coupon_GetDiscountFromValidCouponCode]
    @PKCouponCode varchar(50)
AS
    SELECT * 
    FROM Coupon 
    WHERE CouponCode = @PKCouponCode AND Valid = 1

Here is how the DB looks like:

I encounter an error

Input string was not in a correct format

I don't know what's thing is going wrong, any ideas?

Answer 1

If you want the discount value, then you should return only the discount from the SP (since it is named GetDiscountfrom ...)

SELECT CouponDiscount FROM Coupon WHERE CouponCode = @PKCouponCode AND Valid = 1

This will make it a one-column resultset, which matches the access reader[0] from C#.

The other option is of course to change the C# side to read the second item (index 1) or reference the column by name, eg

r_discountValue = float.Parse(reader[1].ToString());
r_discountValue = float.Parse(reader["CouponDiscount"].ToString());

You would have got Input string was not in a correct format. because it was reading "DIS_77" which float.parse cannot process.

Answer 2

You are using first column ie CouponCode for fetching discount. instead of that you need to use second column ie. couponDiscount

So try something like this

 r_discountValue = float.Parse(reader["CouponDiscount"].ToString());