錯誤：加入3個表

Question

錯誤時指定的轉換無效。這發生在內部加入代碼

string Query = "SELECT User.First, User.Last, Details.Address1, 
         Details.Address2, Details.County, Details.Country, Code.Codenum 
       FROM User INNER JOIN Details on User.Details_DetailsID = Details.DetailsID 
         INNER JOIN Codes on User.Code_ID = Code.ID 
       WHERE User.Last ='" + cbUsers.SelectedItem.ToString() + "'"; 



string snum = myReader.GetInt32(1).ToString(); 
txtcode.Text = snum; 

Answer 1

GetInt32(1)意味着你從你的閱讀器，其被命名爲User.Last第二列的值。我認爲這是可能不能轉換爲Int32的姓氏。