获取在AJAX UpdatePanel中触发回发的ASP.NET控件

Question

与此问题相关：On postback, how can I check which control cause postback in Page_Init event

如果控件包装在ASP.NET AJAX控制中，则变量“UpdatePanel”为空，因为它在AJAX PostBack之后具有不同的ID。有没有解决方案来获取在ASP.NET Ajax UpdatePanel中触发回发的控件？

public static string GetPostBackControlName( Page page ) {
        Control control = null;

        /**
         * First we will check the "__EVENTTARGET" because if the postback is made
         * by controls which used the _doPostBack function, it will be available in the Request.Form collection.
         */
        string ctrlname = page.Request.Params["__EVENTTARGET"];

        if ( !String.IsNullOrEmpty( ctrlname ) ) {
            control = page.FindControl( ctrlname );
        } else {
            /**
             * If __EVENTTARGER is null, the control is a button-type and
             * need to iterate over the form collection to find it.
             */
            Control c = null;
            string ctrlStr = null;

            foreach ( string ctl in page.Request.Form ) {
                if ( ctl.EndsWith( ".x" ) || ctl.EndsWith( ".y" ) ) {
                    /**
                     * ImageButtons have an additional "quasi-property" in their ID which identifies
                     * the mouse-coordinates (X and Y).
                     */
                    ctrlStr = ctl.Substring( 0, ctl.Length - 2 );
                    c = page.FindControl( ctrlStr );
                } else {
                    c = page.FindControl( ctl );
                }

                if ( c is Button || c is ImageButton ) {
                    control = c;
                    break;
                }
            }
        }

        if ( control != null ) {
            return control.ID;
        }

        return string.Empty;
    }

Answer 1

尝试以下方法：

public string GetAsyncPostBackControlID()
{
    string smUniqueId = ScriptManager.GetCurrent(Page).UniqueID;
    string smFieldValue = Request.Form[smUniqueId];

    if (!String.IsNullOrEmpty(smFieldValue) && smFieldValue.Contains('|'))
    {
        return smFieldValue.Split('|')[1];
    }

    return String.Empty;
}

上述方法使用页面上ScriptManager的隐藏字段。通过使用ScriptManager的UniqueID搜索表单键，可以在服务器上访问它的值。隐藏字段中的值的格式为[UpdatePanel UniqueID]|[Postback Control ID]。了解此信息后，我们可以检索启动异步回发的控件的ID。它也适用于提交按钮。

Answer 2

下面是@bugventure在VB.NET中的代码……修改后添加了一个页面引用作为参数，这样我就可以在一个公共库中使用它。

Public Function GetAsyncPostBackControlID(ByRef page As Page) As String
        Dim smUniqueId As String = ScriptManager.GetCurrent(page).UniqueID
        Dim smFieldValue As String = page.Request.Form(smUniqueId)

        If Not String.IsNullOrEmpty(smFieldValue) AndAlso smFieldValue.Contains("|") Then
            Return smFieldValue.Split("|")(1)
        End If

        Return String.Empty
End Function

用法：

' Call from a control or Page
Dim postbackControlID As String = GetAsyncPostBackControlID(Page)

' Call from a page
Dim postbackControlID As String = GetAsyncPostBackControlID(Me)

Answer 3

若要获取导致异步回发的控件，可以使用以下代码而不是分析

var scriptManager = ScriptManager.GetCurrent(Page);
var asyncPostBackSourceControl = Page.FindControl(scriptManager.AsyncPostBackSourceElementID);