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c# connection string and concatenation app.config

I have the following connection string through which i connect to an Access database(.mdb) located in a sub-folder inside the root-folder of my application :
OleDbConnection con = new OledbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + System.AppDomain.CurrentDomain.BaseDirectory() + "Data\rctts.mdb;Jet OLEDB:Database Password=mypassword;")
My question is, how do i put the connection string in the app.config file? Generally, i use :
<connectionStrings>
<add name="Test" connectionString="Data Source=.;Initial Catalog=OmidPayamak;Integrated Security=True" providerName="System.Data.SqlClient" />
</connectionStrings>
The issue i am facing is that in my connection string, i am doing some concatenations and also using System.AppDomain.CurrentDomain.BaseDirectory() to set the Data Source...
How do i do the same concatenation in app.config ? Is it possible to do so ?

You could try the following:
connectionString="Data Source=|DataDirectory|\rctts.mdb;Initial Catalog=OmidPayamak;Integrated Security=True"
and then try to set the value of DataDirectory as below:
var currentDomain = AppDomain.CurrentDomain;
var basePath = currentDomain.BaseDirectory;
currentDomain.SetData("DataDirectory", basePath+"\Data");
at the corresponding startup file of your application.

Although configuration APIs offer no facilities to manipulate connection strings for you, you could place connection string "template" into configuration, and do the rest of manipulation in your code using string.Format:
Config:
<connectionStrings>
<add name="Test" connectionString="Data Source={0}Data\rctts.mdb;Initial Catalog=OmidPayamak;Integrated Security=True" providerName="System.Data.SqlClient" />
</connectionStrings>
C# code:
string conStr = string.Format(
ConfigurationManager.ConnectionStrings["Test"].ConnectionString
, System.AppDomain.CurrentDomain.BaseDirectory()
);

how to put a webhostdatabase connection string in a winform application?

i have myself tried a lot but i couldn't find out what is the problem of my below connection string. i have put both my webhost connection string and winform connection string help please?
<connectionStrings> <add name="ReGdbEntities" connectionString="metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;
provider=System.Data.SqlClient;
provider connection string="data source=.\SQLEXPRESS;
initial catalog=ReGdb;
integrated security=True;
MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" /> </connectionStrings>
and here is my webhostdatabase connectionstring
Data Source=SQL5000322.Smarterasp.net;
Initial Catalog=DB_9BDB7789_ReGdb;
User Id=DB_9BDB7789_ReGdb_admin;
Password=happy;

hey bro you can modify your connection string this way and it must work. just copy and replace it with your connection string
<connectionStrings>
<add name="ReGdbEntities" connectionString="metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;
provider=System.Data.SqlClient;
provider connection tring=quot;
datasource=SQL5000322.Smarterasp.net;
initial catalog=DB_9BDB7789_ReGdb;
User Id=DB_9BDB7789_ReGdb_admin;
Password=happy;
MultipleActiveResultSets=True;
App=EntityFramework""
providerName="System.Data.EntityClient" />
</connectionStrings>
here you go bro it must work

Pay attention to nested quotes:
provider connection string="data source=...

Entity Framework unable to find connection string in nested web.config

I'm new to .NET, but I'm using EntityFramework 5.0 and .NET 4.5
I have a website where the connectionStrings in the web.config are maintained in a configSource as follows:
<connectionStrings configSource="ConfigOverrides\overrideConnectionStrings.config">
</connectionStrings>
My website has modules with nested web.config files. These modules specify their own connectionStrings in the nested web.config. Everything was fine until I put a System.Data.EntityClient connection in my ConfigOverrides\overrideConnectionStrings file. After I did this I would get an error from the module:
No connection string named 'WebsiteEntities' could be found in the application config file.
If I copy the module's connectionString to the one in ConfigOverrides I get an error that there is already a connection string with that name. If I remove the connection string from their nested web.config and just put it in my overrides, it works. However I'm not wanting to maintain all module's connectionSettings in that global override.
Contents of overrideConnectionStrings.config:
<connectionStrings>
<add name="SqlServices" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=my_db;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\my_db.mdf;" />
<add name="TermsEntities" providerName="System.Data.EntityClient" connectionString="metadata=res://*/Terms.csdl|res://*/Terms.ssdl|res://*/Terms.msl;provider=System.Data.SqlClient;provider connection string='data source=(LocalDb)\v11.0;Initial Catalog=my_db;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\my_db.mdf;connect timeout=30;MultipleActiveResultSets=True;App=EntityFramework'" />
<add name="ADServer" connectionString="LDAP://ldap.localdomain:389/DC=company,DC=com" />
</connectionStrings>
Contents of module's nested Web.config connectionStrings:
<connectionStrings>
<add name="WebsiteEntities" connectionString="metadata=res://*/WSE.csdl|res://*/WSE.ssdl|res://*/WSE.msl;provider=System.Data.SqlClient;provider connection string="data source=.;initial catalog=WSE_DB;integrated security=True;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />
<add name="RoutingConn" providerName="System.Data.SqlClient" connectionString="data source=.;initial catalog=WSE_DB;integrated security=True;" />
</connectionStrings>
I should note that the module worked fine until I added my TermsEntities to the main site's web.config (via the ConfigOverrides).

I am still unable to figure out what in my application setup is causing the connectionString to not be found. While debugging I could view the connectionStrings available to the path of the request and I would see all connectionStrings (those in the nested web.config and those in the root web.config).
My workaround is to just use the ConfigurationManager from System.Configuration and read in the connection string :
public partial class WebsiteEntities : DbContext
{
public WebsiteEntities()
: base(ConfigurationManager.ConnectionStrings["WebsiteEntities"].ConnectionString ?? "name=WebsiteEntities")
{
}
...
This seems to be working.

How to set connectionstring at web.config file programmatically or dynamically?

I'm trying to create an ASP.NET website. There I'm using a database. To connect with the database I'm using the connectionstring which I've stored in the web.config file like
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=G:\CarRentalServices\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>
</connectionStrings>
and at code behind
private string _connectionString = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
So you can see the database is stored at G:\path\to\db\CarRentalServiceDB.mdf.
But now if my friend want to take the project from me and try to run the project from his machine then he has to change the connectionString at web.config. Say the website is now at D:\path\to\db\foo\CarRentalServiceDB.mdf in my friend's machine, then the connectionString needs to change. Isn't it tedious?
Is there any way to change the connectionString dynamically with any batch file or code so that it will change with respect to the current directory it is residing now?

You shoud use the |DataDirectory| token: http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring.aspx
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>

You would add multiple connections strings in your web.config file and call the one you need like
Web.config File
<connectionStrings>
<add name="DBConnectionString"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=G:\CarRentalServices\App_Data\CarRentalServiceDB.mdf;Integrated Security=True"/>
<add name="DBConnectionStringTwo"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=D:\path\to\db\foo\CarRentalServiceDB.mdf;Integrated Security=True"/>
</connectionStrings>
Code for connection strings
//Connection String 1
private string _connectionString = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
//Connection String 2
private string _connectionString2 = ConfigurationManager.ConnectionStrings["DBConnectionStringTwo"].ConnectionString;

c# Loading connectionString from file on runtime

I have an application (Console) already in place which is reading connection string from the bin directory.
We are planning to pass a directory path from command line which would point to the configurations.This way we would be able to switch between pointing to different DBs by just changing the command line parameter for "ConfigurationDirectory"
This requires us to dynamically load the connectionstring, the format of my connection string is as below :
<connectionStrings>
<add name="DB1" connectionString="Data Source=DB;Initial Catalog=someCatalog;Persist Security Info=True;User ID=****;Password=****; Asynchronous Processing=true" providerName="System.Data.SqlClient" />
<add name="DB2" connectionString="Data Source=DBName;Initial Catalog=someCatalog2;Persist Security Info=True;User ID=****;Password=****; Asynchronous Processing=true" providerName="System.Data.SqlClient" />
</connectionStrings>
We do not have a configuration tag.
To load up the connection string dynamically I am trying this :
var connectionStringconfigfile = "C:Somepath\connectionstring.config"
ExeConfigurationFileMap configMap = new ExeConfigurationFileMap();
configMap.ExeConfigFilename = connectionStringconfigfile;
Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configMap, ConfigurationUserLevel.None);
config.Save(ConfigurationSaveMode.Modified);
ConfigurationManager.RefreshSection("connectionStrings");
I am unable to use the connectionstring file I have currently because it complains that there is no configuration tag.
The problem is that my code already uses the following to initialize connection string :
ConfigurationManager.ConnectionStrings["DB1"].ConnectionString
With this new approach the above line does not seem to work and always gives me null, is there a way so that I do not have to change my existing code?

If you wrap your external config file in a <configuration> block, like this:
<configuration><br>
<connectionStrings><br>
<add name="DB1" connectionString="Data Source=DB;Initial Catalog=someCatalog;Persist Security Info=True;User ID=****;Password=****; Asynchronous Processing=true" providerName="System.Data.SqlClient" /><br>
<add name="DB2" connectionString="Data Source=DBName;Initial Catalog=someCatalog2;Persist Security Info=True;User ID=****;Password=****; Asynchronous Processing=true" providerName="System.Data.SqlClient" /><br>
</connectionStrings><br>
</configuration>
Your code should work.