GridView排序问题

GridView的Sorting事件,每次e.sortDirection都是升序排序,参考了下别人的解决方案

 

 

 1using System;
 2using System.Data;
 3using System.Configuration;
 4using System.Web;
 5using System.Web.Security;
 6using System.Web.UI;
 7using System.Web.UI.WebControls;
 8using System.Web.UI.WebControls.WebParts;
 9using System.Web.UI.HtmlControls;


public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            this.BindData();
        }
    }
    private DataTable GetData()
    {
        const string sql_select_workorder = "select WorkOrderID,ProductID,OrderQty,StockedQty,ScrappedQty,StartDate,EndDate,DueDate,ScrapReasonID,ModifiedDate from Production.WorkOrder";
        return DBUtility.SqlHelper.ExecuteDataSet(DBUtility.SqlHelper.workOrderConnectionString, sql_select_workorder).Tables[0];
    }
    private void BindData()
    {       
        this.GridView1.DataSource = this.GetData();
        this.GridView1.DataBind();
    }

    protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
    {
        string sortExpression=e.SortExpression;
        DataView dv = new DataView(GetData());
        // 根据视图状态来取排序方向
        if (GridViewSortDirection == SortDirection.Ascending)
        {
            // 如果本次是升序,那么下次将是倒序
            GridViewSortDirection = SortDirection.Descending;
            
            dv.Sort = sortExpression + " desc";
        }
        else
        {
            // 如果本次是倒序,下次将是升序
            GridViewSortDirection = SortDirection.Ascending;
            dv.Sort = sortExpression;
        }
        this.GridView1.DataSource = dv;
        this.GridView1.DataBind();
    }
    public SortDirection GridViewSortDirection
    {
        get 
        {
            // 第一次点击排序时,视图状态为空,将其以倒序排列
            if (ViewState["sortDirection"] == null)
            { ViewState["sortDirection"] = SortDirection.Ascending; }
            return (SortDirection)ViewState["sortDirection"];
        }
        set
        {
            ViewState["sortDirection"] = value;
        }
    }
}