当只有3个表时，SQL数据适配器返回4个表的计数。

Question

我正在通过一个填充一个ComboBox，我遇到了一个问题，在这个问题中，适配器要带回四个表的计数。这很奇怪，因为数据库中只有三个表，它用适当的行填充最终表(ds.Tables3)而不是初始表(ds.Tables)。

以下代码没有填充ComboBox (请注意cboCities.DataSource (第二行到最后一行))：

         private void Form1_Load(object sender, EventArgs e)
    {
        // Establishes a connection to the database.
        SqlCeConnection cn = new SqlCeConnection(@"Data Source = C:\Users\user\Desktop\Projects\ParkSurvey WF\ParkSurvey WF\ParkSurvey.sdf; Persist Security Info = False; Password = *");
        cn.Open();
        // Gathering the names of cities from the Cities database to populate cboCities.
        SqlCeCommand cmd = cn.CreateCommand();
        cmd.CommandText = "SELECT CityId, Name FROM Cities ORDER BY Name ASC";
        SqlCeDataAdapter da = new SqlCeDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        // Closing the connection and setting the data bindings for cboCities.
        cn.Close();
        cboCities.ValueMember = "CityId";
        cboCities.DisplayMember = "Name";
        cboCities.DataSource = ds.Tables[0];
        cboCities.SelectedIndex = -1;
    }

这确实适当地填充了ComboBox (再次注意到cboCities.DataSource)：

        private void Form1_Load(object sender, EventArgs e)
    {
        // Establishes a connection to the database.
        SqlCeConnection cn = new SqlCeConnection(@"Data Source = C:\Users\user\Desktop\Projects\ParkSurvey WF\ParkSurvey WF\ParkSurvey.sdf; Persist Security Info = False; Password = *");
        cn.Open();
        // Gathering the names of cities from the Cities database to populate cboCities.
        SqlCeCommand cmd = cn.CreateCommand();
        cmd.CommandText = "SELECT CityId, Name FROM Cities ORDER BY Name ASC";
        SqlCeDataAdapter da = new SqlCeDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        // Closing the connection and setting the data bindings for cboCities.
        cn.Close();
        cboCities.ValueMember = "CityId";
        cboCities.DisplayMember = "Name";
        cboCities.DataSource = ds.Tables[3];
        cboCities.SelectedIndex = -1;
    }

是什么原因导致我的DataAdapter带回四个表，而不仅仅是城市，为什么要填充第四个表而不是初始表？如果你需要更多的代码样本来帮助我解决这个问题，请告诉我。非常感谢!

Answer 1

如果您填充了一个DataTable而不是一个DataSet，那么它应该可以工作，因为您只选择了一个表。

除此之外，我必须承认，我不知道这种行为的原因。