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Updating Connection String in DLL from Winforms - Linq to SQL

I developed a class library that uses Linq To Sql to communicate with a database.
When I added this I used Server Explorer to add a database and all the tables I want to talk to.
It then built a .dbml file for me.
In the "Designer" file I can see:
public TPDataContext() :
base(global::TPAPI.Properties.Settings.Default.TruePotentialConnectionString, mappingSource)
{
OnCreated();
}
If I update the "Linq to SQL" it regenerates a new designer.cs file
It stored the connection string in Settings.settings with the scope of "Application".
All functions just fine.
But, I have then added a winfoms project that needs to change this setting. So I added the following code:
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.ConnectionStrings.ConnectionStrings["TPAPI.Properties.Settings.TruePotentialConnectionString"].ConnectionString = txtConnectionString.Text;
config.Save(ConfigurationSaveMode.Modified, true);
ConfigurationManager.RefreshSection("connectionStrings");
This updates the connection string in the dll but it only takes effect when the application is shutdown and restarted.
When I am upgrading clients it overwrites what the user had already entered when using it previously.
I cannot seem to work out the best way to:
Not overwrite previous user defined connection string when the app is upgraded.
Be able to save the new connection string and use it without having to stop/start the app.
Having had a read of other threads it appears that the dll shouldn't really have any "local" settings in it (?) and they should all be sent by the winforms app. But, I am unclear on how use Linq to Sql in the dll without it automatically looking/adding it's own connection string.
Can anyone help please?
Thanks

I have decided to rewrite all my DataContext calls to accept the connection string parameter.
I had to amend and test about 40 functions but now the connection string is stored in the winforms application as a user setting and overrides the default connection string generated by Linq to SQL.
So, now in my dll it now looks like
TPDataContext db = new TPDataContext(connStr);
HTH

Not able to persist new changes in appsetting section in app.config WPF?

Below is the code i am using to update or change the values in appsetting in app.config
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings["userName"].Value = username;
config.AppSettings.Settings["pwd"].Value = pwd;
config.Save(ConfigurationSaveMode.Modified, true);
ConfigurationManager.RefreshSection("appSettings");
i am using above code to change or update the settings in appsetting section at runtime and want the changes to persist so that when i run the application it should pick the new values from appsettings but here it doesn't happen so the changes made and saved at run time do not persist when i relaunch my application again it has the old default settings. Also i checked app.config in bin/debug but it too had the old values in appsettings. i refered various blogs and post here too as a reference but it got the same code as above but it did not persist the settings.have referred this post

I had the same problem while ago. I would have preferred to put this in a comment but I don't have that privilege. My answer might not be your case but I think is worth to be shared.
May I ask you where your bin folder is located? Windows 7 when you programmatically alter a file that isn't in a user accessible space creates a copy of that file in a Roaming space and there the file will stay. Every time you try to access the file (like your app.config) W7 transparently redirect your readings/writings to this file, so there's a chance that you are modifying the file in the roaming space, leaving the one you are lookin unaltered.
Are the changes you are making still there the successive time you start the application?
Disclaimer/Apology: I'm not an experienced user so if I am saying silly things let me know and I will remove this comment.

See below(from MSDN) and remember app.config is in your project. .exe.config is the actual file name.
Client applications use a global configuration that applies to all users, separate configurations that apply to individual users, and configurations that apply to roaming users. The userLevel parameter determines the location of the configuration file being opened by indicating whether it has no user level (the configuration file is in the same directory as the application) or has a per-user level (the configuration file is in an application settings path determined by the user level).
Specify which configuration to get by passing one of the following values for userLevel:
To get the Configuration object that applies to all users, set userLevel to None.
To get the local Configuration object that applies to the current user, set userLevel to PerUserRoamingAndLocal.
To get the roaming Configuration object that applies to the current user, set userLevel to PerUserRoaming.
NoteNote
To get the Configuration object for a resource, your code must have read permissions on all the configuration files from which it inherits settings. To update a configuration file, your code must additionally have write permissions for both the configuration file and the directory in which it exists.

i got my solution of above problem, my goal was to persist changes done at run time at application or user level. Initially i tried using App.config where i kept default settings for application in appsettings section of app.config, but later after research i got to refer i got to know appsetting does not persist the changes, instead you can use userSettings section where under YourApplication.Property.Settings you can give your userlevel settings and it worked for me. To do this you do not need to go to App.config to do it manually, rather you can do it from the property window of project.
Right Click on your project -> Select Settings Tab on the left-> Now on the right hand side you will see the Resource section , give the ResourceName, Type, Scope and its value and you are done. The same value can be access and change dynamically from Code as well.
Below are Code Excerpt for the same --
Accessing Settings Value
enter code here
userName = Properties.Settings.Default.UserName;
pwd = Properties.Settings.Default.PWD;
Saving New Settings Back
enter code here
Properties.Settings.Default.UserName = userName.ToString();
Properties.Settings.Default.PWD = newPWD..ToString();
Properties.Settings.Default.Save();
And when you will launch your application next time you will get the new changed settings as your default settings.
I hope that helps
Thanks Guys
VJ

Issues on dynamically change and switching the connectionString in web Config

I am trying to switch different databases for a web application at Run time.
Senario
We have one asp.net web application and different databases for different customers.I am trying to switch particular connection string value from a common database where i am keeping a mapping table for connection string ,particular customer id and password .After the successful lo gin i am piking a connection string from the common database and edit the web.config file connection string section by replacing selected connection string at run time.
i am doing this by add following code to login event
conectionString = cString;
Configuration openWebConfiguration = WebConfigurationManager.OpenWebConfiguration("~");
ConnectionStringsSection sections = openWebConfiguration.GetSection("connectionStrings") as ConnectionStringsSection;
if (sections != null)
{
sections.ConnectionStrings["ConnectionStringName"].ConnectionString = conectionString;
ConfigurationManager.RefreshSection("ConnectionStringName");
openWebConfiguration.Save();
}
i am reading above connection string on a page by using ConfigurationManager.problem is the web config file is changing but after calling to another page using Response.Redirect will throw an exception .Exception is "Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack "I can realized this is something happen on cross threaded environment.My questions are
What is exact reason for above exception?
which page life circle of the Asp.net reads the setting from the web config file ?
What is the proper way i can implement above scenario?

I am wondering why this question seems still unanswered.OK i have found some answermy self.It may be wrong but some how they are giving some meaning to me.I assume following are acceptable for my knowledge level.
1)I don't know the exact reason ,but this is something happen because of code is modified while an application running
2)Based on my search WEB Config file is started to read by the application when the IIS server start.So what ever values to be modified inside WEB Config ,require to restart the IIS server to load them in to memory.We can modify the connection string dynamically but still the application will run on the previous connection string.So we need t restart the IIS to load newer one.
Note:Modify a existing connection string is different than add a new connection string to a WEB Config.
3)I have used a common data Base where i have authentication details for different different connection strings for Several database.WeB config has the connection string for above master database.If an user gives his authentication detail it will select his connection string and load it as new connection string .So the remaining process will be based on that connection string.
Any new arguments for above answers are highly appreciable.I need corrections from other developers because i am very eager to learn.

Saving setting to a exe

I have a program which I want to store information in a string. I have been using the Properties.Setting.Default.STRINGname to store the information, which works fine on my PC, and I can see the saved strings (when I go to the settings in the application). But when I take the application to a new PC it losses the strings. Is there a way to be able to edit this information and save it in the app? So basically I need to be able to convert the user setting to application setting, but after the runtime.
var settings = Properties.Settings.Default;
settings.H1 = textbox1.text;
settings.H2 = textbox2.text;
settings.Save();

MSDN explicit says something about this:
Settings that are application-scoped are read-only, and can only be changed at design time or by altering the .config file in between application sessions. Settings that are user-scoped, however, can be written at run time just as you would change any property value. The new value persists for the duration of the application session. You can persist the changes to the settings between application sessions by calling the Save method.
For this, Application setting will never work for you. However, if you are using a User scoped settings it does work, but soon you change the application from one computer to another (as you say you want to) you will loose the settings as that's another machine (another user-scope)...
There are way to continue to have the same settings, you can do, at least 2 things:
use a .config file to save the settings (it's an XML file)
use a service to host the settings and you can read if user has internet access
What you can't do is
using only one executable file, save the settings from computer to computer.

User settings are compiled differently than Application settings, and thus cannot be converted after compilation. Why not compile with Application Settings?

The code you are using should save the user settings. Rememeber that user settings will be saved in the user's data folder. Not in the configuration file where the app was installed (say program files). This is the usual path:
<Profile Directory>\<Company Name>\<App Name>_<Evidence Type>_<Evidence Hash>\<Version>\user.config
See this links form more information

How to conditionally suppress an asp:MenuItem from the default ASP.NET Web Site master?

I need to let an unprofessional to be able to install an ASP.NET application by himself.
The installer (a person) will copy the application files into a virtual directory.
The installer will get a SQL server name username and password suitable for creating a database from the sysadmin.
The application has a web page which is automatically creating an empty database on a designated SQL server which its name is given by the installer who is setting the server's name using a specific web-form.
I would like to have the installation page to appear on the master menu only once.
The installation page has a link in the master as an asp:MenuItem .
Which is the best SIMPLE way to suppress this menu item after the database installation?
I thought of a specific variable in Web.config, which will hold the value stating if the database is already installed and ready to be use or not, but some doesn't like this solution.

This gives you a range of options:
Nine Options for Managing Persistent User State in Your ASP.NET Application
You could use the appSettings section in the Web.Config file to generate variables at project or folder level and cache the vars for the duration of the session:
<appSettings>
<add key="customsetting1" value="Some text here"/>
</appSettings>
System.Configuration.Configuration rootWebConfig1 =
System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(null);
if (rootWebConfig1.AppSettings.Settings.Count > 0)
{
System.Configuration.KeyValueConfigurationElement customSetting =
rootWebConfig1.AppSettings.Settings["customsetting1"];
if (customSetting != null)
Console.WriteLine("customsetting1 application string = \"{0}\"",
customSetting.Value);
else
Console.WriteLine("No customsetting1 application string");
}
More info: http://msdn.microsoft.com/en-us/library/ms228154.aspx