请教怎么修改配置文件app.config的值

请问如何修改配置文件app.config的值

传入的参数为  
modifyXml( "IntervalTime ",   "60 ");
     
我的方法      
private   void   modifyXml(string   xmlkey,   string   xmlvalue)
                {
                        Assembly   ass   =   Assembly.GetExecutingAssembly();
                        string   fullPath   =   ass.Location.Substring(0,   ass.Location.LastIndexOf(@ "\ "));
                        fullPath   =   fullPath   +   @ "\CareHealth.vshost.exe.config ";
                        //MessageBox.Show(fullPath);
                        XmlDocument   xmldoc   =   new   XmlDocument();
                        xmldoc.Load(fullPath);
                        XmlNodeList   xnlist   =   xmldoc.SelectSingleNode( "configuration ").ChildNodes;

                        foreach   (XmlNode   xn   in   xnlist)
                        {
                                XmlElement   xe   =   (XmlElement)xn;
                                if   (xe.InnerXml.IndexOf( " <add   key=\ " "   +   xmlkey   +   "\ " ")   !=   -1)
                                {
                                        xe.SetAttribute( "value ",   xmlvalue);
                                        break;
                                }
                        }
                        xmldoc.Save(fullPath);
                }


配置文件
<?xml   version= "1.0 "   encoding= "utf-8 "   ?>
<configuration>
        <configSections>
                <sectionGroup   name= "applicationSettings "   type= "System.Configuration.ApplicationSettingsGroup,   System,   Version=2.0.0.0,   Culture=neutral,   PublicKeyToken=b77a5c561934e089 "   >
                        <section   name= "CareHealth.Settings1 "   type= "System.Configuration.ClientSettingsSection,   System,   Version=2.0.0.0,   Culture=neutral,   PublicKeyToken=b77a5c561934e089 "   requirePermission= "false "   />

                </sectionGroup>
        </configSections>
       
    <appSettings>
        <add   key= "IntervalTime "   value= "3600000 "   />
       
    </appSettings>
</configuration>


谢谢，请帮忙！


[解决办法]
App.config也是一个xml文件
按照xml文件的操作处理就行
[解决办法]
给你一段我这边已经运行过的代码：
1.读取配置文件：
private System.Xml.XmlDocument xDoc = null;
/// <summary>
/// 获取key值
/// </summary>
/// <param name= "AppKey "> key名称 </param>
/// <returns> key值 </returns>
private string GetConfigKeyValue(string AppKey)
{
string path = " ";
XmlNode xNode;
XmlElement xElem;
try
{
path = Application.StartupPath + "\\TagsValueTransForm.exe.config ";
if(xDoc == null)
{
xDoc = new System.Xml.XmlDocument();
xDoc.Load(path);
}
}
catch(Exception)
{
throw new Exception( "未发现配置文件： "+path);
}

try
{
xNode = xDoc.SelectSingleNode( "//appSettings ");
xElem = (XmlElement)xNode.SelectSingleNode( "//add[@key= ' " + AppKey + " '] ");
if ( xElem != null )
return xElem.GetAttribute( "value ");else
return " ";
}
catch(Exception ex)
{
throw ex;
}
}

2。修改配置文件：
/// <summary>
/// 修改配置文件
/// </summary>
/// <param name= "AppKey "> key名称 </param>
/// <param name= "AppValue "> key值 </param>
private void UpdateConfig(string AppKey, string AppValue)
{
string path = " ";
XmlNode xNode;
XmlElement xElem;
try
{
path = Application.StartupPath + "\\TagsValueTransForm.exe.config ";
if(xDoc == null)
{
xDoc = new System.Xml.XmlDocument();
xDoc.Load(path);
}
}
catch(Exception)
{
throw new Exception( "未发现配置文件： "+path);
}

try
{
xNode = xDoc.SelectSingleNode( "//appSettings ");
xElem = (XmlElement)xNode.SelectSingleNode( "//add[@key= ' " + AppKey + " '] ");
if ( xElem != null ) xElem.SetAttribute( "value ",AppValue);
xDoc.Save(path);
}
catch(Exception ex)
{
throw ex;
}
}