ASP Gridview无法加载视图状态。

Question

当我在GridView.ROWDATABOUND事件中动态创建按钮时，我在asp.net 4.5中收到错误。

按钮代码：

Dim btn1 As New Button()
btn1.ID = "btn1"
btn1.Width = "50"
btn1.Text = "Edit"
btn1.CssClass = "AdminPageBtn"
btn1.CommandName = "Edit"
btn1.CommandArgument = "Edit"
btn1.Enabled = True

e.Row.Cells（e.Row.Cells.Count - 1）.Controls.Add（btn1）

我也在使用AJAX 4.0，使用脚本管理器和更新面板。

该按钮执行以下方法

Protected Sub gvwRoutes_RowEditing(ByVal sender As Object, 
                      ByVal e As System.Web.UI.WebControls.GridViewEditEventArgs)
                Handles gvwRoutes.RowEditing
End Sub

执行时，出现错误：

Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request. For example, when adding controls dynamically, the controls added during a post-back must match the type and position of the controls added during the initial request.

需要解决方案..！

Answer 1

如果您尝试在控件集合中的某个位置添加控件，那么您肯定会遇到视图状态问题。根据Asp.net中动态控件的MSDN specification

Inserting a dynamic control somewhere other than the end of the Controls collection 
can cause a corrupted view state

所以可能的解决方法是使用页面中的Placeholder添加动态控件。这将在Control集合的中间保留索引，并且还将处理View状态。由于新添加的控件将具有来自占位符控件的视图状态。