C# Asp.Net 使用 DropDownList 更改 GridView 的 DataSource

Question

我创建了一个网页来显示本地数据库中存储的数据。我想使用 DropDownList Item 来更改 GridView 中的列和顺序。从下拉列表中选择或更改查询字符串时更改 DataGrid 数据源会更容易吗？

所有数据都是从同一个数据源中提取的，但是显示不同的列和不同的顺序。

例如：

DropdownList Selctions 是（General Overview、portfolio、System Log）

选择一般概览后： GridView 将显示 Columns([name],[Location],[Profit],[Currentstandings] Ordered by Name asending From Tabel[Main])

在选择投资组合时：

GridView 会显示

Column([name],[Current Standings],[profit],[Price],[Quantity Bought],[Buy/Sell] 按从 Table[main] 降序的利润排序)

选择系统日志时：

gridview 会显示

Column([Time],[System Message],[Error Code], [Restart] 按时间排序，从表[System Log]开始)

任何帮助将不胜感激！我已经搜索了两天没有结果的答案。欢迎提出想法！！谢谢！

Answer 1

只要您在 GridView 中保留属性 AutoGenerateColumns="true"（这是默认值）并且不设置任何 <Columns>。 GridView 将自动生成适合您数据源的列。下面作为一个简单的例子

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true">
    <asp:ListItem>NameOnly</asp:ListItem>
    <asp:ListItem>WithPosition</asp:ListItem>
</asp:DropDownList>
<br />
<asp:GridView runat="server" ID="GridView1">
</asp:GridView>

代码隐藏

protected void Page_Load(object sender, EventArgs e)
{
    if (DropDownList1.SelectedValue == "WithPosition")
    {
        GridView1.DataSource = new List<dynamic>() {
            new { Name = "Andy", LastName="Wayne", Position = "PG"},
            new { Name = "Bill", LastName="Johnson", Position = "SD" },
            new { Name = "Caroline", LastName="Barry", Position = "Manager"}
        };
        GridView1.DataBind();
    }
    else if (DropDownList1.SelectedValue == "NameOnly")
    {
        GridView1.DataSource = new List<dynamic>() {
            new { Name = "Andy", LastName = "Wayne"},
            new { Name = "Bill", LastName = "Johnson"},
            new { Name = "Caroline", LastName = "Barry"}
        };
        GridView1.DataBind();
    }
}

Answer 2

为了使用组合框来更改选定的dataTbale。我的列表项设置为：“常规”、“利润”、“系统日志”。我在表单中插入了一个数据网格，然后没有设置数据源，在 c# 端编写了这段代码

private void drop1_SelectedIndexChanged(object sender, EventArgs e)
        {
            String selI = drop1.SelectedItem.ToString();
            String strConnect = ("Data Source = (LocalDB)\\MSSQLLocalDB; AttachDbFilename = C:\\Users\\smith\\Documents\\SqlStockDB.mdf; Integrated Security = True; Connect Timeout = 30");
            SqlConnection Connect = new SqlConnection(strConnect);
            SqlCommand sqlcmd = new SqlCommand();
            sqlcmd.Connection = Connect;
            sqlcmd.CommandType = CommandType.Text;

            if (selI == "General")
            {
                sqlcmd.CommandText = "SELECT [Call Sign] AS Call_Sign, [Current Price] AS Current_Price FROM [Main] ORDER BY [Call Sign]";

                SqlDataAdapter adp = new SqlDataAdapter(sqlcmd);

                DataTable dtRecord = new DataTable();
                adp.Fill(dtRecord);
                dataGridView1.DataSource = dtRecord;
                dataGridView1.Refresh();
            }
            dataGridView1.ClearSelection();

            if (selI == "Profit")
            {
                sqlcmd.CommandText = "SELECT [Call Sign] AS Call_Sign, [Current Price] AS Current_Price, [Profit], [Buy], [Sell], [Available Money] AS Available_Money, [Quantity Bought] AS Quantity_Bought FROM [Main] ORDER BY [Profit] DESC, [Quantity Bought] DESC, [Call Sign]";

                SqlDataAdapter adp = new SqlDataAdapter(sqlcmd);

                DataTable dtRecord = new DataTable();
                adp.Fill(dtRecord);
                dataGridView1.DataSource = dtRecord;
                dataGridView1.Refresh();
            }

            if (selI == "System Logs")
            {
                sqlcmd.CommandText = "SELECT [Time], [Module], [Error Code] AS Error_Code, [Restart] FROM [Error] ORDER BY [Time], [Module], [Restart]";

                SqlDataAdapter adp = new SqlDataAdapter(sqlcmd);

                DataTable dtRecord = new DataTable();
                adp.Fill(dtRecord);
                dataGridView1.DataSource = dtRecord;

                dataGridView1.Refresh();
            }

从列表中选择一个项目后，它现在将在网格上显示不同的数据集，而无需尝试调用不同的数据源。