C# 位置0处没有行

Question

我再次收到错误，指出没有与 SQL 查询匹配的行。

它指出:

There is no row at position 0.

点在:

 firstnameTxt.Text = dt.Rows[0].ItemArray[1].ToString();

以下是我的C#代码。

    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["New"] != null)
        {
            redPnl.Visible = false;
            UserNameSess.Text += Session["New"].ToString();

            SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0; AttachDbFilename=C:\Users\Donald\Documents\Visual Studio 2013\Projects\DesktopApplication\DesktopApplication\Student_CB.mdf ;Integrated Security=True");
            con.Open();

            SqlDataAdapter sda = new SqlDataAdapter("Select Student_Username, Student_FName, Student_SName, Student_Email FROM Student Where Student_Username=@StuUsername", con);
            sda.SelectCommand.Parameters.Add("@StuUsername", SqlDbType.VarChar).Value = UserNameSess.Text;
            DataTable dt = new DataTable();
            sda.Fill(dt);
            if (dt.Rows.Count > 0)

            usernameTxt.Text = dt.Rows[0].ItemArray[0].ToString();
            firstnameTxt.Text = dt.Rows[0].ItemArray[1].ToString();
            surnameTxt.Text = dt.Rows[0].ItemArray[2].ToString();
            emailTxt.Text = dt.Rows[0].ItemArray[3].ToString();
            dt.Clear();

        }
        else
        {
            redPnl.Visible = true;
        }



    }

我不知道它为什么要这样做，因为它诚实地带回了值(value)并将其显示在文本框中。

Answer 1

您忘记将大括号添加到您的 if 子句中:

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["New"] != null)
    {
        redPnl.Visible = false;
        UserNameSess.Text += Session["New"].ToString();

        SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0; AttachDbFilename=C:\Users\Donald\Documents\Visual Studio 2013\Projects\DesktopApplication\DesktopApplication\Student_CB.mdf ;Integrated Security=True");
        con.Open();

        SqlDataAdapter sda = new SqlDataAdapter("Select Student_Username, Student_FName, Student_SName, Student_Email FROM Student Where Student_Username=@StuUsername", con);
        sda.SelectCommand.Parameters.Add("@StuUsername", SqlDbType.VarChar).Value = UserNameSess.Text;
        DataTable dt = new DataTable();
        sda.Fill(dt);
        if (dt.Rows.Count > 0)
        {  
           usernameTxt.Text = dt.Rows[0].ItemArray[0].ToString();
           firstnameTxt.Text = dt.Rows[0].ItemArray[1].ToString();
           surnameTxt.Text = dt.Rows[0].ItemArray[2].ToString();
           emailTxt.Text = dt.Rows[0].ItemArray[3].ToString();
           dt.Clear();
        }
    }
    else
    {
        redPnl.Visible = true;
    }
}