asp.net – 从用户控件内添加页面控件集合

Public Class WebUserControl1
    Inherits System.Web.UI.UserControl

        Private Sub UC_Init(ByVal sender As Object,ByVal e As System.EventArgs) Handles Me.Init
            AddHandler Me.Page.Init,AddressOf Me.Page_Init
        End Sub

        Private Sub Page_Init(ByVal sender As Object,ByVal e As EventArgs)
            Dim dialogDiv As New Panel
            dialogDiv.ID = "DialogDiv"
            If Not Page.Form.Controls.Contains(dialogDiv) Then
                Page.Form.Controls.AddAt(0,dialogDiv)
            End If
        End Sub

    End Class

How to implement it in C#. I’m always getting the error The control
collection cannot be modified on Load,PreRender
I need a Literal Control to be added to my master page’s head from a user control. The literal control will contain the css link.

是否要将文字添加到主文件中的HeadContent-ContentPlaceHolder控件或页面的标题(html头元素)？但是,我在这里展示了两者.

这是UserControl的代码隐藏：

public partial class UC_AddToMaster : System.Web.UI.UserControl
{
    private void Page_Init(object sender,System.EventArgs e)
    {
        this.Page.Init += UC_AddToMaster_Init;
    }

    private void UC_AddToMaster_Init(object sender,EventArgs e)
    {
        Literal literal = new Literal{ Text = "Hi World!" };
        // if you want to add it to the header of the page:
        if (!Page.Header.Controls.Contains(literal))
        {
            Page.Header.Controls.AddAt(0,literal);
        }

        // if you want to add it to the master's HeadContent ContentPlaceHolder control:
        var siteMaster = Page.Master as SiteMaster;
        if (siteMaster != null)
        {
            if (!siteMaster.Head.Controls.Contains(literal))
            {
                siteMaster.Head.Controls.AddAt(0,literal);
            }
        }
    }
}

对于上面提到的HeadContent方法,我在master中提供了以下属性：

// in the master
public ContentPlaceHolder Head { get { return this.HeadContent; } }

因此,我需要在UserControl中将页面的主文件转换为它的实际类型(SiteMaster here).否则我无法访问此属性.