用sql數據填充GridView

Question

我需要從我的用戶表中選擇具有我將必須從下拉列表中獲得的roleID的用戶的用戶名。數據沒有出現在GridView中。看不出有什麼問題，請幫助我。 已經嘗試過2種方式

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     SqlConnection con = new SqlConnection(cs); 
     con.Open(); 
     SqlCommand cmd = new SqlCommand("select username from tblUser where roleID like '" + DropDownList1.SelectedValue + "'", con); 

     SqlDataAdapter da = new SqlDataAdapter(cmd); 
     DataTable dt = new DataTable(); 
     da.Fill(dt); 
     GridView2.DataSource = dt; 
     GridView2.DataBind(); 
     con.Close(); 
    } 

protected void Button2_Click(object sender, EventArgs e) 
{ 
    SqlConnection con = new SqlConnection(cs); 
    con.Open(); 
    SqlCommand cmd = new SqlCommand("select username from tblUser where roleID like '" + DropDownList1.SelectedValue + "'", con); 

    SqlDataReader reader = cmd.ExecuteReader(); 

    GridView2.DataSource = reader; 
    GridView2.DataBind(); 
    con.Close(); 
} 

Answer 1

好了，所以對我來說這一個工作。你也必須檢查來源。就像我的GridView發生了什麼，它說AutoGenerateColumns = false，我刪除它。這一切都奏效了！

protected void Button2_Click(object sender, EventArgs e) 
{ 
    string cs = ConfigurationManager.ConnectionStrings["roleDB"].ConnectionString; 
    SqlConnection con = new SqlConnection(cs); 
    con.Open(); 
    SqlCommand cmd = con.CreateCommand(); 
    cmd.CommandType = CommandType.Text; 
    cmd.CommandText = "select username from tblUser where roleID like '" + DropDownList1.SelectedValue + "'"; 
    SqlDataAdapter da = new SqlDataAdapter(cmd); 
    DataTable dt = new DataTable(); 
    da.Fill(dt); 
    GridView2.DataSource = dt; 
    GridView2.DataBind(); 
    con.Close(); 
}