Question

我想访问gridview中的下拉列表并将其选定的值保存到数据库中，但它不断给出错误，即对象引用未设置为对象的实例。

void Gridview1_RowUpdating用于使用图像按钮将值从gridview编辑保存到数据库。

下拉列表的html ID是gridview中的“DropDownList1”。还有其他选择吗？

C＃：

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    try
    {
        con2.Open();
        using (con2)
        {
            DropDownList RoomID = e.RowIndex.FindControl("DropDownList1") as DropDownList;                  
            string query = "UPDATE Info SET Forename=@Forename,LastName=@LastName,Email=@Email,Phone=@Phone,RoomID=@RoomName WHERE ID=@ID";
            SqlCommand sqlCmd = new SqlCommand(query, con2);
            sqlCmd.Parameters.AddWithValue("@Forename", (GridView1.Rows[e.RowIndex].FindControl("txtForeName") as TextBox).Text.Trim());
            sqlCmd.Parameters.AddWithValue("@LastName", (GridView1.Rows[e.RowIndex].FindControl("txtLastName") as TextBox).Text.Trim());
            sqlCmd.Parameters.AddWithValue("@Email", (GridView1.Rows[e.RowIndex].FindControl("txtEmail") as TextBox).Text.Trim());
            sqlCmd.Parameters.AddWithValue("@Phone", (GridView1.Rows[e.RowIndex].FindControl("txtPhone") as TextBox).Text.Trim()); 
            sqlCmd.Parameters.AddWithValue("@RoomName",Convert.ToInt32(RoomID.SelectedValue)); 
            sqlCmd.Parameters.AddWithValue("@ID",Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString())); 


            sqlCmd.ExecuteNonQuery();
            GridView1.EditIndex = -1;
            PopulateGridView();
            lblSuccessMessage.Text = "Selected Record Updated!";
            lblErrorMessage.Text = "";
            con2.Close();
        }


    }
    catch (Exception ex)
    {

        lblSuccessMessage.Text = "";
        lblErrorMessage.Text = ex.Message;

    }
}

Answer 1

e.RowIndex是int，你不会在那里找到DropDownList。你需要

DropDownList RoomID = GridView1.Rows[e.RowIndex].FindControl("DropDownList1") as DropDownList;

.Net对象引用未设置为Dropdownlist的对象实例

1 个答案: