对webconfig文件中的connectingtring的修改，其它节点的修改都可以参考。

 

private   void  WriteConfigFile( string  FilePath)
         ... {
            if (!File.Exists(string.Format("{0}/{1}", m_strAssemblyPath, FilePath)))
            ...{
                MessageBox.Show("Web配置文件丢失，请尝试重新安装解决该问题。", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }

            XmlDocument document = new XmlDocument();
            document.Load(string.Format("{0}/{1}", m_strAssemblyPath, FilePath));
            XmlNode appSettingNode = document.SelectSingleNode("/configuration/connectionStrings");
            XmlNode dbConnectionNode = document.SelectSingleNode("/configuration/connectionStrings/add[@name='" + ConnectionStringNodeName + "']");
            if (dbConnectionNode != null)
            ...{
                dbConnectionNode.Attributes["connectionString"].Value = GetConnectionString();
                dbConnectionNode.Attributes["providerName"].Value = ProviderName;
            }
            else
            ...{
                XmlElement elementAdd = document.CreateElement("add");
                XmlAttribute keyAttribute = document.CreateAttribute("name");
                keyAttribute.Value = ConnectionStringNodeName;
                XmlAttribute valueAttribute = document.CreateAttribute("connectionString");
                valueAttribute.Value = this.m_connection.ConnectionString;
                XmlAttribute providerAttribute = document.CreateAttribute("providerName");
                providerAttribute.Value = ProviderName;
                elementAdd.Attributes.Append(keyAttribute);
                elementAdd.Attributes.Append(valueAttribute);
                elementAdd.Attributes.Append(providerAttribute);
                appSettingNode.AppendChild(elementAdd);
            }
            document.Save(FilePath);
        }