價值被給予mysql命令參數，但它不返回正確的ID

Question

下面是在程序中執行查詢的一個例子：

 Int64 kooid = new Int64(); 
     myCommand.CommandText = ("SELECT kooiid FROM kooien where NummerExtern =?NummerExtern"); 
     myCommand.Parameters.Add("?NummerExtern", MySqlDbType.Int64).Value = kooi.Kooinr; 
     kooid = Convert.ToInt64(myCommand.ExecuteScalar()); 
     return kooid; 

此處是組成一個例子表妝

kooiid(int)| kooidlistppg(int)|quarantaine(tiny int) |idvogelsoort(int)|idvogelondersoort(int)| vasteoflossekooie(tiny int)| bezetofniet(tiny int)| idsponsor(int)| NummerExtern(int) 

之前u向當我manualy運行查詢它的功能，但也即使kooinr變量是正確的查詢返回零kooiid當由PROGRAMM有序

Answer 1

發現解決方案

Int64 kooid = new Int64(); 
     myCommand.CommandText = ("Select kooiid from kooien where NummerExtern = ?NummerExtern"); 
     myCommand.Parameters.Add("?NummerExtern", MySqlDbType.Int64).Value = kooi.Kooinr; 
     string kooidstring = myCommand.ExecuteScalar().ToString(); 
     kooid = Convert.ToInt64(kooidstring); 
     return kooid;