数据更改时下拉列表未更新

Question

我有一个数据绑定的类别下拉列表。从中选择填充网格视图。当我删除一个类别时，它会成功更新我的产品网格视图（不显示任何条目），但不会更新类别的下拉列表，直到我重新运行程序。

我的页面加载：

protected void Page_Load(object sender, EventArgs e)
    {
        // Check if loaded for first time.
        if (!IsPostBack)
        {
            // Bind the data displayed in the Dropdownlists.
            Login.SelectAllCat(DropListCat);

        }
    }

我删除类别的代码：

protected void BtnDeleteCat_Click(object sender, EventArgs e)
    {
        try
        {
            // Get int id from selectioin in drop down list.
            int id = Convert.ToInt32(DropListCat.SelectedValue.ToString());
            // Call method to open data base, create command from stored procedure and delete item to database.
            Login.DeleteCategory(id);
            // Update the data displayed in the Dropdownlists.
            Login.SelectAllCat(DropListCat);


        }
        catch (NullReferenceException)
        {
            LblProdId.Text = "No Category Selected!";
        }
    }

我的下拉列表：

<asp:DropDownList ID="DropListCat" runat="server" BackColor="#66FFFF"
            Width="200px" AutoPostBack="True" AppendDataBoundItems="True">
</asp:DropDownList>

我的连接和绑定代码。在 Login class.

// Method to select all categories and display them in dropdown lists.
public static void SelectAllCat(DropDownList list)
{
    // SqlConnection.
    SqlConnection con = new SqlConnection(conString);
    // Create new command and parameterise.
    SqlCommand cmd = new SqlCommand();
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.CommandText = "SelectAllCat";
    //
    // Adapted from
    // Source link: http://www.c-sharpcorner.com/UploadFile/abhikumarvatsa/data-binding-to-dropdownlist-and-listbox-in-Asp-Net/
    //
    cmd.Connection = con;
    try
    {
        // Open connection and bind data to GUI.
        con.Open();

        list.DataSource = cmd.ExecuteReader();
        list.DataTextField = "CatName";
        list.DataValueField = "CatID";
        list.DataBind();

    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        con.Close();
        con.Dispose();
    }
}

我的存储过程：

CREATE PROCEDURE SelectAllProd
AS
    SELECT * FROM Prod;
GO

这是我尝试删除类别后的结果。
当我重新运行这个项目的时候，这个类就已经被删除了。

编辑

实际上，它是删除类别，但它保留了页面加载时的原始数据绑定。所以我想我需要弄清楚如何擦除它。

Answer 1

我通过在重新绑定数据之前清除下拉列表项来修复它，如下所示：

// Method to select all categories and display them in dropdown lists.
    public static void SelectAllCat(DropDownList list)
    {
        // Clear any previously bound items.
        list.Items.Clear(); 
        // etc.../

Answer 2

写

    DropListCat.DataBind();

在BtnDeleteCat_Click

数据更改时下拉列表未更新

Drop down list not updated when data changed

c#

asp.net

data-binding

webforms

sql-server-2014