GridView升序排序不起作用

Question

我有一个启用排序的GridView。 对于单页结果，升序和降序都可以正常工作。 但是当有多个页面时，单独降序效果很好。 排序也有效，但是当我单击下一页时，它再次变为未排序。 我不知道问题是由于排序方向还是页面调度。 请帮助。 以下是代码：

protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
    GridView grid = sender as GridView;
    //Retrieve the table from the session object.
    DataTable dt = Session["List"] as DataTable;

    if (dt != null)
    {
        //Sort the data.
        dt.DefaultView.Sort = e.SortExpression + " " + GetSortDirection(e.SortExpression);
        grid.DataSource = Session["List"];
        grid.DataBind();
    }
}

private string GetSortDirection(string column)
{
    string sortDirection = "ASC";      
    string sortExpression = ViewState["SortExpression"] as string;
    if (sortExpression != null)
    {
        if (sortExpression == column)
        {
            string lastDirection = ViewState["SortDirection"] as string;
            if ((lastDirection != null) && (lastDirection == "ASC"))
            {
                sortDirection = "DESC";
            }
        }
    }
    // Save new values in ViewState.
    ViewState["SortDirection"] = sortDirection;
    ViewState["SortExpression"] = column;
    return sortDirection;
}

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    GridView1.PageIndex = e.NewPageIndex;
    GridView1.DataSource = bindGridView();
    GridView1.DataBind();
}

Answer 1

您可以使用会话变量来存储最新的排序表达式，并在下次对网格进行排序时，将网格的排序表达式与存储最后一个排序表达式的Session变量进行比较。 如果两列相等，则检查上一个排序的方向，然后按相反的方向排序。

DataTable sourceTable = GridAttendence.DataSource as DataTable;
DataView view = new DataView(sourceTable);
string[] sortData = Session["sortExpression"].ToString().Trim().Split(' ');
if (e.SortExpression == sortData[0])
 {
if (sortData[1] == "ASC")
{
    view.Sort = e.SortExpression + " " + "DESC";
    this.ViewState["sortExpression"] = e.SortExpression + " " + "DESC";
}
else
{
    view.Sort = e.SortExpression + " " + "ASC";
    this.ViewState["sortExpression"] = e.SortExpression + " " + "ASC";
}
 }
 else
{
view.Sort = e.SortExpression + " " + "ASC";
this.ViewState["sortExpression"] = e.SortExpression + " " + "ASC";
 }

Answer 2

经过如此多的研究，我为自己的问题找到了正确的答案。 这可能会在将来对某人有所帮助。 将以下代码添加到bindGridView（）

if (ViewState["sortExpr"] != null)
{
     dv = new DataView(ds.Tables[0]);
     dv.Sort = (string)ViewState["sortExpr"];
}
else
    dv = ds.Tables[0].DefaultView;

和

#region Sorting
    protected void Gridview1_Sort(object sender, GridViewSortEventArgs e)
    {
        ViewState["sortExpr"] = e.SortExpression + " " + GetSortDirection(e.SortExpression); 
        Gridview1.DataSource = bindGridView();
        Gridview1.DataBind();
    }

    private string GetSortDirection(string column)
    {
        // By default, set the sort direction to ascending.
        string sortDirection = "ASC";

        // Retrieve the last column that was sorted.
        string sortExpression = ViewState["SortExpression"] as string;

        if (sortExpression != null)
        {
            // Check if the same column is being sorted.
            // Otherwise, the default value can be returned.
            if (sortExpression == column)
            {
                string lastDirection = ViewState["SortDirection"] as string;
                if ((lastDirection != null) && (lastDirection == "ASC"))
                {
                    sortDirection = "DESC";
                }
            }
        }
        // Save new values in ViewState.
        ViewState["SortDirection"] = sortDirection;
        ViewState["SortExpression"] = column;

        return sortDirection;
    }
    #endregion