DataRow未显示

Question

我使用了DataRow，它可以在我的WinForm中的组合框中显示但不知何故，它不起作用，尽管整个表格已成功显示在gridview中。

   private void Form1_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection();
        SqlCommand cmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();
        DataSet ds = new DataSet();

        con.ConnectionString = "Data Source=.;Initial Catalog=StudentDetails;Integrated Security=True";
        cmd.Connection = con;
        cmd.CommandText = "select * from StuDet";
        da.SelectCommand = cmd;
        da.Fill(ds);

        dt = ds.Tables[0];
        dataGridView1.DataSource = dt;

        DataRow dr = dt.NewRow();
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            comboBox1.Items.Add(dr[0]);
        }
    }

Answer 1

您创建一个空的新行

DataRow dr = dt.NewRow();

并将其Rows.Count次添加到comboBox1。我想你想要的是通过dt.Rows中的每一行：

foreach (DataRow dr in dt.Rows)
{
    comboBox1.Items.Add(dr["Roll"]);
}

Answer 2

  

刚才想出答案，请看看底部的循环。

   private void Form1_Load(object sender, EventArgs e)
    {
        SqlConnection con = new SqlConnection();
        SqlCommand cmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();
        DataSet ds = new DataSet();

        con.ConnectionString = "Data Source=.;Initial Catalog=StudentDetails;Integrated Security=True";
        cmd.Connection = con;
        cmd.CommandText = "select * from studet";
        da.SelectCommand = cmd;
        da.Fill(ds);

        dt = ds.Tables[0];
        dataGridView1.DataSource = dt;
 ////////////////////////////////////////////////////

        DataRow dr = dt.NewRow();
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            dr[0] = dt.Rows[i][0];
            comboBox1.Items.Add(dr[0]);
        }
    }