read,write and update connectionstring in app.config file at run time in C#

Question

I have created a form for connection settings, where user can update server name, datatbase and user id and password. I have stored my connection string in app.config file.

My problem is, how can I update connection string in app.config file at run time and How can I change the information of the conectionstring through the text box on the form in the first time, the text box will display information of server name, id, password after the first time

here my app.config

    <?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
            <section name="Data123.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
        </sectionGroup>   
    </configSections>
  <connectionStrings>
   <add name="Data123Entities" connectionString="metadata=res://*/Data123DB.csdl|res://*/Data123DB.ssdl|res://*/Data123DB.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=nguyenduyhai;initial catalog=Data123;persist security info=True;user id=sa;password=1234567;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
    <!--<add name="Data123Entities" connectionString="metadata=res://*/Data123DB.csdl|res://*/Data123DB.ssdl|res://*/Data123DB.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=NGUYENDUYHAI\SQLEXPRESS;initial catalog=Data123;persist security info=True;user id=sa;password=1234567;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />-->
  </connectionStrings>
</configuration>

here the code that i am trying but not work , please help me

     void saveconect(string address,string id,string pass)
{

            var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            var connectionStringsSection = (ConnectionStringsSection)config.GetSection("connectionStrings");
            connectionStringsSection.ConnectionStrings["Data123Entities"].ConnectionString = "data source=" + address + ";initial catalog=" + "Data123" + ";user id=" + id + ";password=" + pass + "";
            config.Save(ConfigurationSaveMode.Modified, true);
            ConfigurationManager.RefreshSection("connectionStrings");
}




 private void buttonUpdate_Click(object sender, EventArgs e)
    {


        saveconect(textboxServerAddress.Text, textBoxUserID.Text, textBoxPassword.Text);
    }

Answer 1

Have you tried to run application in release folder? Because in Debug mode won't change.

Answer 2

With using System.Xml.Linq; it will be something like:

var doc = XElement.Load(fileName); 
var target = doc.Element("configuration").Elements("configurationStrings").Where(e => e.Element("name").Value == "Data123Entities").Single(); 
target.Element("connectionString").Value = "metadata=res://*/Data123DB.csdl|res://*/Data123DB.ssdl|res://*/Data123DB.msl;provider=System.Data.SqlClient;provider connection string="data source=" + dataSource + ";initial catalog=" + initCatalog + ";persist security info=True;user id=sa;password=1234567;MultipleActiveResultSets=True;App=EntityFramework""
doc.Save(fileName);