对DataTable字符串列进行排序,但底部为null/empty

Question

我需要通过一个字符串值的列对DataTable或DataGridView进行排序,但在排序ASCENDING时在BOTTOM中使用null/empty值.

DataTable没有填充SQL语句,因此没有订单.

如果我做

DataGridView1.Sort(New RowComparer(System.ComponentModel.ListSortDirection.Ascending))

然后它抛出一个异常,说DataGridView是DataBound,这是正确的,但对我没有帮助,我想保持它的数据绑定.

它是.NET 2.0,这意味着没有LINQ可用!

Answer 1

在某些情况下,如果表中还有另一列,则可以执行此操作:

SELECT completed, completed IS NULL AS isnull
FROM TABLE
ORDER BY isnull DESC, completed DESC

编辑:
在VB.NET中像这样

        For Each srSearchResult In srcSearchResultCollection

            Try
                dr = dt.NewRow()
                dr("cn") = srSearchResult.GetDirectoryEntry().Properties("cn").Value
                dr("Account") = srSearchResult.GetDirectoryEntry().Properties("sAMAccountName").Value
                dr("Nachname") = srSearchResult.GetDirectoryEntry().Properties("sn").Value
                dr("Vorname") = srSearchResult.GetDirectoryEntry().Properties("givenname").Value
                dr("Mail") = srSearchResult.GetDirectoryEntry().Properties("mail").Value
                dr("HomeDirectory") = srSearchResult.GetDirectoryEntry().Properties("homedirectory").Value
                dr("LogonScript") = srSearchResult.GetDirectoryEntry().Properties("scriptPath").Value

                dr("IsNull") = String.IsNullOrEmpty(dr("Nachname").ToString())

                dt.Rows.Add(dr)
            Catch ex As Exception

            End Try

        Next srSearchResult
dt.DefaultView.Sort = "IsNull ASC, Nachname ASC"

Answer 2

Davide Piras有一个很好的解决方案,但是我有另一个最简单的解决方案

添加一个新列,只需一行即可完成

// just, add a new column
ActualDataTable.Columns.Add("NullEmptyCheck", typeof(int), "ColumnNameToSort is Null OR ColumnNameToSort = ''");

// apply sort expression
ActualDataTable.DefaultView.Sort = "NullEmptyCheck asc, ColumnNameToSort asc";
// pass datasource to grid
MyGridView.DataSource = ActualDataTable.DefaultView;
MyGridView.DataBind();