SharePoint 用SafeControl的方式创建能够重复利用的Control

1)：假设我们有这样一个场景，我们为不同组的pages定义了不同的Layout，并且我们要在每个Layout中放置不同的可以修改Footer信息。

2)：这里的实现方式是创建一个List，然后在List中添加不同的Item，每个Item包含Layout中的Footer信息，然后在SharePoint 中用SafeControl的方式创建能够重复利用的Control。

如下为具体实现方式：

1)：创建Control，这里定义了一些参数，指定从哪个List中的哪个Item的哪个Field中获取信息

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Microsoft.SharePoint;

namespace EricSunProject.WebParts.WebControls
{
    [DefaultProperty("ListName")]
    [ToolboxData("<{0}:FnxDisclosureControl runat=server></{0}:FnxDisclosureControl>")]
    public class FnxDisclosureControl : WebControl
    {
        /// <summary>
        /// The name of the disclosure list
        /// </summary>
        [Bindable(true)]
        public string ListName
        {
            get
            {
                String s = (String)ViewState["ListName"];
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                ViewState["ListName"] = value;
            }
        }

        /// <summary>
        /// The key field name to retrieve the disclosure text
        /// </summary>
        [Bindable(true)]
        public string DisclosureField
        {
            get
            {
                String s = (String)ViewState["DisclosureField"];
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                ViewState["DisclosureField"] = value;
            }
        }

        /// <summary>
        /// The disclosure text field name
        /// </summary>
        [Bindable(true)]
        public string DisclosureTextField
        {
            get
            {
                String s = (String)ViewState["DisclosureTextField"];
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                ViewState["DisclosureTextField"] = value;
            }
        }

        /// <summary>
        /// The unique disclosure key value
        /// </summary>
        [Bindable(true)]
        public string DisclosureUniqueName
        {
            get
            {
                String s = (String)ViewState["DisclosureUniqueName"];
                return ((s == null) ? String.Empty : s);
            }

            set
            {
                ViewState["DisclosureUniqueName"] = value;
            }
        }
        
        protected override void CreateChildControls()
        {
            base.CreateChildControls();

            if (!string.IsNullOrEmpty(this.DisclosureUniqueName) && !string.IsNullOrEmpty(this.ListName) &&
                !string.IsNullOrEmpty(this.DisclosureField) && !string.IsNullOrEmpty(this.DisclosureTextField))
            {
                SPWeb rootWeb = SPContext.Current.Site.RootWeb;
                if (rootWeb != null)
                {
                    SPList disclosureList = rootWeb.Lists[this.ListName];
                    if (disclosureList != null)
                    {
                        SPQuery query = new SPQuery();
                        query.Query = string.Format("<Where><Eq><FieldRef Name=\"{0}\" /><Value Type=\"Text\">{1}</Value></Eq></Where>", this.DisclosureField, this.DisclosureUniqueName);
                        SPListItemCollection items = disclosureList.GetItems(query);

                        if (items.Count > 0)
                        {
                            SPListItem contentItem = items[0]; // query should only return 1 item.
                            string htmlContent = contentItem != null ? contentItem[this.DisclosureTextField] as string : string.Empty;
                            this.Controls.Add(new Literal() { Text = htmlContent });
                        }
                    }
                }
            }
        }
    }
}

2)：在package中声明此SafeControl

<?xml version="1.0" encoding="utf-8"?>
<Solution xmlns="http://schemas.microsoft.com/sharepoint/">
  <Assemblies>
    <Assembly Location="EricSunProject.WebParts.dll" DeploymentTarget="GlobalAssemblyCache">
      <SafeControls>
        <SafeControl Assembly="EricSunProject.WebParts, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1de19275c7811c3b" Namespace="EricSunProject.WebParts.WebControls" TypeName="FnxDisclosureControl" />
      </SafeControls>
    </Assembly>
  </Assemblies>
</Solution>

3)：在对应的Layout中注册此Control

<%@ Register Tagprefix="EricSunControls" Namespace="EricSunProject.WebParts.WebControls" Assembly="EricSunProject.WebParts, Version=1.0.0.0, Culture=neutral, PublicKeyToken=1de19275c7811c3b" %>

4)：应用此Control

             <div class="footnote">
                <EricSunControls:FnxDisclosureControl ID="FnxPageFooter" ListName="FNX Disclosures" DisclosureField="FnxDisclosureType" DisclosureTextField="FnxDisclosureText" DisclosureUniqueName="Home Page Disclosure" runat="server" />
            </div>

这样就做到了这个Control可以重复利用，并且只需要改变参数，标识应用哪个List中的哪个Item中的哪个Field，去填充信息。当然了 SharePoint中的Item的值是可以随时修改的，这样后续只需要修改SharePoint中Item对应的Field值，那么我们自定义的Pages就可以随时显示修改后的Footer等信息。