c# - 值被赋予 mysql 命令中的参数，但它没有返回正确的 id

Question

以下是程序中执行的查询的示例:

        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;

这里是餐 table 妆容的一个例子

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

在你问我手动运行查询时它会起作用，但是当程序很好地排序时，即使kooinr变量是正确的，查询也会向kooiid返回零

Answer 1

找到了解决办法

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;