Connection String at run time

This is how you can make connection string dynamic: 

Use the settings.settings to store and create the connection string ( which updates also the app.config ), then  change the code of the settings.cs (to create this file automatically simply hit the button "View Code" in the setting designer buttons bar) ovveriding public override object this[string propertyName]

Assuming the setting name for your connection string is "ConStr"

  internal sealed partial class Settings {

       

        public Settings() 

        {

             // To add event handlers for saving and changing settings, uncomment the lines below:

            // this.SettingChanging += this.SettingChangingEventHandler;

           

              // this.SettingsSaving += this.SettingsSavingEventHandler;

            //

        }

       

        private void SettingChangingEventHandler(object sender, System.Configuration.SettingChangingEventArgs e) 

       {

            // Add code to handle the SettingChangingEvent event here.

        }

       

        private void SettingsSavingEventHandler(object sender, System.ComponentModel.CancelEventArgs e) 

        {

            // Add code to handle the SettingsSaving event here.

        }

 

        public override object this[string propertyName]

        {

         get

         {

          if (propertyName == "ConnStr")

          {

           return GetConStr(); // GetConStr retrive the run time value for the connection string

          }

          return base[propertyName];

         }

         set

         {

          base[propertyName] = value;

         }

        }

 

    private string GetConnStr()

    {

     string connstr;

     // build your connStr here

     return connStr;

    }

    }