如何保持网格视图的排序状态？(升序和降序)

Question

我有一个问题已经困扰了我很长一段时间，由于我是 .NET 的初学者，我迫切需要帮助。

我正在使用网格视图来显示查询结果。但是，我不是将其直接注入实体/LINQ 数据源，而是手动编码加载、排序和分页等事件。问题出在排序中，我无法保持升序/降序状态。我能想到的可能的解决方案之一是缓存状态，但是，我觉得还有另一种更整洁的方法。因此，你们能给我推荐其他更适合的想法吗？

提前非常感谢！下面是我用于排序的代码。显然，无论我单击列标题多少次，e.SortDirection始终等于ascending。

switch (e.SortExpression)
        {
            case "Album":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.DocumentAlbum.Name ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.DocumentAlbum.Name descending
                                     select doc;
                break;
            case "Category":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.DocumentCategory.Name ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.DocumentCategory.Name descending
                                     select doc;
                break;
            case "Title":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.Title ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.Title descending
                                     select doc;
                break;
            case "Description":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.Description ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.Description descending
                                     select doc;
                break;
            case "DateCreated":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.DateCreated ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.DateCreated descending
                                     select doc;
                break;
            case "DateUpdated":
                if (e.SortDirection == SortDirection.Ascending)
                    _orderedResult = from doc in _result
                                     orderby doc.DateUpdated ascending
                                     select doc;
                else
                    _orderedResult = from doc in _result
                                     orderby doc.DateUpdated descending
                                     select doc;
                break;
        }

Answer 1

实际上，我刚刚找到了答案。我使用 ViewState 函数来跟踪状态。这是我使用的函数：

private SortDirection GetSortDirection(string column)
    {
        // By default, set the sort direction to ascending
        SortDirection _sortDirection = SortDirection.Ascending;
        // 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 = SortDirection.Descending;
                }
            }
        }
        // Save new values in ViewState.
        ViewState["SortDirection"] = _sortDirection.ToString();
        ViewState["SortExpression"] = column;
        return _sortDirection;
    }

Answer 2

protected void gvOfflineSub_Sorting(object sender, GridViewSortEventArgs e)
    {
        IList<SellerDetails> Ilist = gvOfflineSub.DataSource as IList<SellerDetails>;
        DataTable dt = ToDataTable<SellerDetails>(Ilist);
        if (dt != null)
        {
            DataView dataView = new DataView(dt);
            dataView.Sort = e.SortExpression + " " + ConvertSortDirectionToSql(e.SortDirection);
            gvOfflineSub.DataSource = dataView;
            gvOfflineSub.DataBind();
        }
    }
    /// <summary>
    /// Description:Following Method is for Sorting Gridview.
    /// </summary>
    /// <param name="sortDirection"></param>
    /// <returns></returns>
    private string ConvertSortDirectionToSql(SortDirection sortDirection)
    {
        string newSortDirection = String.Empty;
        switch (sortDirection)
        {
            case SortDirection.Ascending:
                newSortDirection = "ASC";
                break;
            case SortDirection.Descending:
                newSortDirection = "DESC";
                break;
        }
        return newSortDirection;
    }

Answer 3

如果您使用的是 LINQ，那么排序非常简单就像这样绑定网格

var data = (from d in edc.TableName
                select new
                {
                    d.Address,
                    d.InsertedDate,                        
                    d.ID
                }).OrderByDescending(d => d.ID);
    if (data != null)
    {
        grdList.DataSource = data;
        grdList.DataBind();
    }