I want a Master UserControl (a Master page, but for UserControls)

问题

ASP.NET master pages - essential things.

However, I have a lot of very similar UserControls in my projects - it might be a standard layout for an AJAX ModalPopup, or something more involved.

I wish I could get rid of some of my duplicated code (both in ascx files and code-behind) with some Master UserControls.

Does anyone have any suggestions of a way to achieve this?

回答1:

The closest thing I can suggest for what you are looking for is a templated custom control. Unfortunately, sharing controls across projects is a lot easier if those things are custom controls, without an ascx file.

回答2:

this is an old question but i have a robust solution for anyone who stumbles upon this.

in app_code, create a file and paste this code:

namespace MasterControls
{
    // code written by alexander taylor on 2011-08-22. http://www.alexsapps.com

    public abstract class ChildUserControl : UserControl
    {
        Control master;

        public abstract string MasterControlVirtualPath { get; }

        protected override void OnInit(EventArgs e)
        {
            master = LoadControl(MasterControlVirtualPath);
            Controls.Add(master);

            base.OnInit(e);
        }

        protected override void Render(HtmlTextWriter writer)
        {
            master.RenderControl(writer);
        }
    }
    public class ControlContentPlaceHolder : Control
    {
        protected override void Render(HtmlTextWriter writer)
        {
            ControlContent found = null;

            foreach (Control c in NamingContainer.NamingContainer.Controls)
            {
                ControlContent search;
                search = c as ControlContent;
                if (search != null && search.ControlContentPlaceHolderID.Equals(ID))
                {
                    found = search;
                    break;
                }
            }

            if (found != null)
            {                
                //write content of the ContentControl
                found.RenderControl(writer);
            }
            else
            {
                //use default content
                base.Render(writer);
            }
        }
    }
    public class ControlContent : Control
    {
        public string ControlContentPlaceHolderID { get; set; }
    }

}

example "master control" (equivalent of master page)

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="MasterControl1.ascx.cs" Inherits="MasterControl1" %>
<%@ Register Namespace="MasterControls" TagPrefix="masterControls" %>

<p>content 1 below:<br />
<masterControls:ControlContentPlaceHolder ID="myContent1" runat="server">
    default content 1 here!
</masterControls:ControlContentPlaceHolder></p>

<p>content 2 below:<br />
<masterControls:ControlContentPlaceHolder ID="myContent2" runat="server">
    default content 2 here!
</masterControls:ControlContentPlaceHolder></p>

example "child control" (equivalent of page)

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="ChildControl1.ascx.cs" Inherits="Control1" %>
<%@ Register Namespace="MasterControls" TagPrefix="masterControls" %>

<masterControls:ControlContent ControlContentPlaceHolderID="myContent1" runat="server">
    custom content 1
</masterControls:ControlContent>

<masterControls:ControlContent ControlContentPlaceHolderID="myContent2" runat="server">
    custom content 2
</masterControls:ControlContent>

in the code behind of the child control

using MasterControls;

//you must inherit the ChildUserControl class!
public partial class Control1 : ChildUserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    public override string MasterControlVirtualPath
    {
        //below, type the location to the master control
        //you wish to apply to this control
        get { return "~/MasterControl1.ascx"; }
    }
}

回答3:

I managed to get this to work using the following code:

public class MasterLoader : UserControl
{
    MasterUserControl _masterUserControl;

    protected override void CreateChildControls()
    {
        Controls.Clear();
        base.CreateChildControls();

        Controls.Add(MasterControl);
    }

    protected override void AddedControl(Control control, int index)
    {
        if (control is MasterUserControl)
            base.AddedControl(control, index);
        else
            MasterControl.ContentArea.Controls.Add(control);
    }

    private MasterUserControl MasterControl
    {
        get
        {
            if (_masterUserControl== null)
                _masterUserControl= (MasterUserControl)LoadControl("~/MasterUserControl.ascx");

            return _masterUserControl;
        }
    }
}

Child user controls inherit from the MasterLoader class. The master user control included a placeholder control that I exposed as a public property called ContentArea.

public partial class MasterUserControl: UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    public PlaceHolder ContentArea 
    {
        get
        {
            return phContent;
        }
    }
}

Event binding and view state work as expected without any changes to any of the user controls.

回答4:

Inheritance. You build the base control as a base class, and then inherit from it.

回答5:

You could also place nested user control on a place holder control in a "master" user control. Use Load method that accepts virtual path to ascx file to load appropriate control.

来源：https://stackoverflow.com/questions/334204/i-want-a-master-usercontrol-a-master-page-but-for-usercontrols