c# - 在 asp.net 的 Gridview 中应用列过滤

Question

我有一个gridview，它在运行时填充了一个表，其中包含未知数量的列，这些列是事先不知道的。

我想使用下拉列表对所有列应用列过滤。

我怎样才能实现它。使用 Jquery、Linq 或简单的 C 语言编码。

public partial class DetailView : System.Web.UI.Page
{
    public static int y = 0;

    public static String colName = "";
    public static Boolean flag = false;
    static String folder = "";
    static public MySqlConnection conn = null;
    static public DropDownList dp = null;

    protected override void OnInit(EventArgs e)
    {

            base.OnInit(e);
            string strcon = ConfigurationManager.ConnectionStrings["abc"].ConnectionString;
            conn = new MySqlConnection(strcon);
            conn.Open();
            Response.Write(Session["cols"].ToString());
            Response.Write(Session["id"].ToString());
            //  Response.Write("qw");
            folder = Session["folderName"].ToString();
            colName = Session["cols"].ToString();


            GridBind(folder, colName, flag);

    }
    protected void Page_Load(object sender, EventArgs e)
    {



    }

    public void GridBind(String folder, String colName, Boolean val)
    {   
        GridView1.DataSource = null;
        GridView1.DataBind();
        GridView1.Columns.Clear();
        y = 0;


        MySqlDataAdapter da;
        if (val == false)
        {

            da = new MySqlDataAdapter("select * from " + folder + "", conn);
        }
        else
        {
            da = new MySqlDataAdapter("select * from " + folder + " where abc= '" + colName + "'", conn);
        }

        DataTable dt = new DataTable();


        da.Fill(dt);



        foreach (DataColumn coloumn in dt.Columns)
        {

            if (!coloumn.ColumnName.Equals("emp"))
            {


                var linkF = new TemplateField();
                linkF.HeaderText = coloumn.ColumnName;
                linkF.HeaderTemplate = new LinkColumn(ListItemType.Header, coloumn.ColumnName,folder);
                linkF.ItemTemplate = new LinkColumn(ListItemType.Item, coloumn.ColumnName,folder);


                GridView1.Columns.Add(linkF);

            }
            else if (coloumn.ColumnName.Equals("emp"))
            {
                //Response.Write("Came");
                BoundField bfield = new BoundField();

                ////Initalize the DataField value.
                bfield.DataField = coloumn.ColumnName;

                ////Initialize the HeaderText field value.
                bfield.HeaderText = coloumn.ColumnName;
                GridView1.Columns.Add(bfield);




            }

        }

            GridView1.DataSource = dt;


            GridView1.DataBind();

    }


    class LinkColumn : DetailView, ITemplate
    {
        int id;
        ListItemType _item;
        String colN = null;
        String fold;
        public LinkColumn(ListItemType item, String colNa, String f)
        {
            _item = item;
            colN = colNa;
            fold = f;
        }
        public void InstantiateIn(System.Web.UI.Control container)
        {

            switch (_item)
            {
                case ListItemType.Header:
                    DetailView.dp = new DropDownList();
                    Label lb = new Label();
                    MySqlCommand cm = new MySqlCommand("select distinct " + colN + " from " + fold + "", conn);

                    MySqlDataAdapter ad = new MySqlDataAdapter();
                    DataTable d = new DataTable();
                    ad.SelectCommand = cm;
                    ad.Fill(d);
                    DetailView.dp.DataTextField = colN;
                    DetailView.dp.DataValueField = colN;
                    DetailView.dp.DataSource = d;
                    DetailView.dp.DataBind();
                    lb.Text = colN.ToUpperInvariant();
                    dp.AutoPostBack = true;
                    dp.EnableViewState = true;
                    //    DetailView.dp.ID = y.ToString();
                    y++;
                    container.Controls.Add(lb);

                    container.Controls.Add(DetailView.dp);
                    //   DetailView.dp.ID = DetailView.y.ToString();
                    //    Response.Write(_Default.dp.ID);
                    DetailView.dp.SelectedIndexChanged += new EventHandler(dp_Selected);


                    break;
                case ListItemType.Item:
                    TextBox tb1 = new TextBox();
                    tb1.Enabled = false;
                    tb1.DataBinding += new EventHandler(tb1_Data);
                    tb1.Columns = 30;
                    container.Controls.Add(tb1);
                    break;
            }

        }

        void tb1_Data(object sender, EventArgs e)
        {
            TextBox txt = (TextBox)sender;
            GridViewRow cont = (GridViewRow)txt.NamingContainer;
            object dataV = DataBinder.Eval(cont.DataItem, colN);
            if (dataV != DBNull.Value)
            {
                txt.Text = dataV.ToString();
            }
        }

        void dp_Selected(object sender, EventArgs e)
        {

            DataTable a = new DataTable();
            DropDownList list = (DropDownList)sender;
            String name = list.SelectedValue;
            // String ID = list.ID.ToString();
            // Session["id"] = ID;
            Session["cols"] = name;
            DetailView.colName = Session["cols"].ToString();
            DetailView.flag = true;
            //   Response.Write(DetailView.colName);


            GridBind(fold, DetailView.colName, true);

        }
    }
}

When i am calling GridBind function from event handler it is giving Null pointer Excpetion at GridView1.DataSource = null;

我的 GridView1 存在于 DetailView.aspx }

任何帮助都将受到高度赞赏

谢谢