string appSetting = txtAppSetting.Text;//appSetting子节点值

string connectionString = txtConnectionString.Text;//连接字符串

string key = txtKey.Text;//appSetting子节点Key

string connectionName = txtConnectionName.Text;//连接Name

ConfigurationOperator op = new ConfigurationOperator(); 

op.SetAppSetting(key, appSetting); 

op.SetConnectionString(connectionName, connectionString); 

op.Save();