对web.config进行新增修改删除读取操作

1.建立一个class，ReadWriteConfig.cs

using System;
using System.Configuration;
using System.Reflection;
using System.Web;
using System.Xml;
public enum ConfigFileType
{
    WebConfig,
    AppConfig
}

namespace WebApplication1
{
    /**//// <summary>
    /// Summary description for ReadWriteConfig.
    /// </summary>
    public class ReadWriteConfig
    {        
        public string docName = String.Empty; 
        private XmlNode node=null;    
        private int _configType;  
        public int ConfigType
        {
            get{ return _configType; }
            set{ _configType=value; }
        }  

        SetValue#region SetValue
        public bool SetValue(string key, string value)
        {
            XmlDocument cfgDoc = new XmlDocument();
            loadConfigDoc(cfgDoc);   
            // retrieve the appSettings node   
            node =  cfgDoc.SelectSingleNode("//appSettings");      
            if( node == null )
            {
                throw new InvalidOperationException( "appSettings section not found");
            }     
            try  
            {   
                // XPath select setting "add" element that contains this key       
                XmlElement addElem= (XmlElement)node.SelectSingleNode("//add[@key='" +key +"']") ;
                if(addElem!=null)
                {
                    addElem.SetAttribute("value",value);
                }    
                // not found, so we need to add the element, key and value   
                else
                {
                    XmlElement entry = cfgDoc.CreateElement("add");
                    entry.SetAttribute("key",key);    
                    entry.SetAttribute("value",value);    
                    node.AppendChild(entry);
                }   
                //save it   
                saveConfigDoc(cfgDoc,docName);   
                return true;  
            }  
            catch
            {
                return false;
            } 
        }  
        
        #endregion

        saveConfigDoc#region saveConfigDoc
        private void saveConfigDoc(XmlDocument cfgDoc,string cfgDocPath)
        {
            try
            {
                XmlTextWriter writer = new XmlTextWriter( cfgDocPath , null ); 
                writer.Formatting = Formatting.Indented;    
                cfgDoc.WriteTo( writer );    
                writer.Flush(); 
                writer.Close();  
                return;
            }  
            catch
            {
                throw;
            }
        } 
        
        #endregion

        removeElement#region removeElement
        public bool removeElement (string elementKey) 
        { 
            try  
            {   
                XmlDocument cfgDoc = new XmlDocument(); 
                loadConfigDoc(cfgDoc);  
                // retrieve the appSettings node  
                node =  cfgDoc.SelectSingleNode("//appSettings");   
                if( node == null )
                {
                    throw new InvalidOperationException( "appSettings section not found");
                }     
                // XPath select setting "add" element that contains this key to remove      
                node.RemoveChild( node.SelectSingleNode("//add[@key='" +elementKey +"']") ); 
                saveConfigDoc(cfgDoc,docName);  
                return true; 
            } 
            catch
            {
                return false;
            } 
        }        
        #endregion

        modifyElement#region modifyElement
        public bool modifyElement (string elementKey) 
        { 
            try  
            {   
                XmlDocument cfgDoc = new XmlDocument(); 
                loadConfigDoc(cfgDoc);  
                // retrieve the appSettings node  
                node =  cfgDoc.SelectSingleNode("//appSettings");   
                if( node == null )
                {
                    throw new InvalidOperationException( "appSettings section not found");
                }     
                // XPath select setting "add" element that contains this key to remove      
                node.RemoveChild(node.SelectSingleNode("//add[@key='" +elementKey +"']")); 
                saveConfigDoc(cfgDoc,docName);  
                return true; 
            } 
            catch
            {
                return false;
            } 
        }        
        #endregion

        loadConfigDoc#region loadConfigDoc
        private XmlDocument loadConfigDoc( XmlDocument cfgDoc ) 
        {   
            // load the config file   
            if(  Convert.ToInt32(ConfigType)==Convert.ToInt32(ConfigFileType.AppConfig))
            {
                docName= ((Assembly.GetEntryAssembly()).GetName()).Name;   
                docName +=   ".exe.config";
            } 
            else
            {
                docName=HttpContext.Current.Server.MapPath("web.config");
            }  
            cfgDoc.Load( docName );  
            return cfgDoc;
        } 
        #endregion
    }
}

2.建立测试页面
2.1 html

<HTML>
    <HEAD>
        <title>WebForm1</title>
        <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
        <meta name="CODE_LANGUAGE" Content="C#">
        <meta name="vs_defaultClientScript" content="JavaScript">
        <meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
    </HEAD>
    <body MS_POSITIONING="GridLayout">
        <form id="Form1" method="post" runat="server">
            <asp:Button id="Button1" style="Z-INDEX: 101; LEFT: 296px; POSITION: absolute; TOP: 120px" runat="server"
                Text="删除"></asp:Button>
            <asp:Button id="Button2" style="Z-INDEX: 102; LEFT: 232px; POSITION: absolute; TOP: 120px" runat="server"
                Text="新增"></asp:Button>
            <asp:Label id="Label1" style="Z-INDEX: 103; LEFT: 104px; POSITION: absolute; TOP: 32px" runat="server">key</asp:Label>
            <asp:TextBox id="TextBox1" style="Z-INDEX: 104; LEFT: 168px; POSITION: absolute; TOP: 32px" runat="server"></asp:TextBox>
            <asp:Label id="Label2" style="Z-INDEX: 105; LEFT: 104px; POSITION: absolute; TOP: 96px" runat="server">value</asp:Label>
            <asp:TextBox id="TextBox2" style="Z-INDEX: 106; LEFT: 168px; POSITION: absolute; TOP: 80px" runat="server"></asp:TextBox>
            <asp:Button id="Button3" style="Z-INDEX: 107; LEFT: 360px; POSITION: absolute; TOP: 120px" runat="server"
                Text="修改"></asp:Button>
        </form>
    </body>
</HTML>

2.2 cs代码

public class WebForm1 : System.Web.UI.Page
    {
        protected System.Web.UI.WebControls.Button Button1;
        protected System.Web.UI.WebControls.Label Label1;
        protected System.Web.UI.WebControls.TextBox TextBox1;
        protected System.Web.UI.WebControls.Label Label2;
        protected System.Web.UI.WebControls.TextBox TextBox2;
        protected System.Web.UI.WebControls.Button Button3;
        protected System.Web.UI.WebControls.Button Button2;
    
        private void Page_Load(object sender, System.EventArgs e)
        {
            
        }

        Web Form Designer generated code#region Web Form Designer generated code
        override protected void OnInit(EventArgs e)
        {
            //
            // CODEGEN: This call is required by the ASP.NET Web Form Designer.
            //
            InitializeComponent();
            base.OnInit(e);
        }
        
        /**//// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {    
            this.Button1.Click += new System.EventHandler(this.Button1_Click);
            this.Button2.Click += new System.EventHandler(this.Button2_Click);
            this.Button3.Click += new System.EventHandler(this.Button3_Click);
            this.Load += new System.EventHandler(this.Page_Load);

        }
        #endregion

        private void Button2_Click(object sender, System.EventArgs e)
        {
            //新增
            ReadWriteConfig config = new ReadWriteConfig();   
            config.ConfigType = (int)ConfigFileType.WebConfig; 
            config.SetValue(this.TextBox1.Text,this.TextBox2.Text);
        }

        private void Button1_Click(object sender, System.EventArgs e)
        {
            //删除
            ReadWriteConfig config = new ReadWriteConfig();   
            config.ConfigType = (int)ConfigFileType.WebConfig; 
            config.removeElement(this.TextBox1.Text);
        }

        private void Button3_Click(object sender, System.EventArgs e)
        {
            //修改
            ReadWriteConfig config = new ReadWriteConfig();   
            config.ConfigType = (int)ConfigFileType.WebConfig; 
            config.SetValue(this.TextBox1.Text,this.TextBox2.Text);
        }
    }