Hi rohanp,

Since the web.config file is common for all the subdomains, you can add multiple connection string in the web.config file like below for each sub domain.

<connectionStrings>
    <add name ="subdomain1" connectionString="Server=.;DataBase=Test;UID=sa;PWD=sa" providerName="System.Data.SqlClient" />
    <add name ="subdomain2" connectionString="Server=.;DataBase=Test;UID=sa;PWD=sa" providerName="System.Data.SqlClient" />
    <add name ="subdomain3" connectionString="Server=.;DataBase=Test;UID=sa;PWD=sa" providerName="System.Data.SqlClient" />
</connectionStrings>

Then you can check for the current url using the below code.

string url = HttpContext.Current.Request.Url.AbsoluteUri;

Then retrive the subdomain from the url. Then use the proper connection string as per the subdomain.

Solution is perfect but  if later few more connection strings are added then i ll need to do add connections in my code behind because i am using configuration manager to get connection string in code behind 

Hi rohanp,

Refer the below article.

Change (Modify) connection string in Web.Config at Runtime in ASP.Net using C# and VB.Net