Question

I am trying to return a value from a SQL database. However everytime I execute the following method I get an error stating, “InvalidCastException was unhandled. Object cannot be cast from DBNull to other types.”

Any light you could shed on this would be greatly appreciated. The method I am using is as follows.

Thanks.

    public static int ScrapTotal2(string prdTypeV, string startDateV, string prtCodeV)
    {
        int scrapTotal2;

        SqlParameter prdType = new SqlParameter("@prdType", SqlDbType.VarChar);
        prdType.Value = prdTypeV;
        SqlParameter startDate = new SqlParameter("@startDate", SqlDbType.VarChar);
        startDate.Value = startDateV;
        SqlParameter prtCode = new SqlParameter("@prtCode", SqlDbType.VarChar);
        prtCode.Value = prtCodeV;

        SqlCommand scrapTotal2SC = new SqlCommand("SELECT SUM([QTY_SCRP]) FROM [TBL_PRDMST] WHERE [PRD_CODE] LIKE @prdType AND [PRD_DATE] = @startDate AND [PRT_CODE] LIKE @prtCode", DataAccess.myConnection);
        scrapTotal2SC.Parameters.Add(prdType);
        scrapTotal2SC.Parameters.Add(startDate);
        scrapTotal2SC.Parameters.Add(prtCode);

        DataAccess.myConnection.Open();
        scrapTotal2 = Convert.ToInt32(scrapTotal2SC.ExecuteScalar());
        DataAccess.myConnection.Close();

        return scrapTotal2;
    }

Answer 1

Your SELECT statement returns NULL value. You have to check if it is null first:

object result = scrapTotal2SC.ExecuteScalar();
if (result == DBNull.Value) 
{ 
    /* write your code */ 
}
else
{
    scrapTotal2 = Convert.ToInt32(result);
}