How to create a connection string in asp.net c#

Question

I am working on asp.net c# project, for connection I used:

SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True");

but I want to get this connection string to get configure and be like this, so can any one help how to create this kind of connection.

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["itmall"].ConnectionString);

Answer 1

Demo :

<connectionStrings>
<add name="myConnectionString" connectionString="server=localhost;database=myDb;uid=myUser;password=myPass;" />
</connectionStrings>

Based on your question:

<connectionStrings>
    <add name="itmall" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=D:\19-02\ABCC\App_Data\abcc.mdf;Integrated Security=True;User Instance=True" />
    </connectionStrings>

Refer links:

http://www.connectionstrings.com/store-connection-string-in-webconfig/

Retrive connection string from web.config file:

write the below code in your file where you want;

string connstring=ConfigurationManager.ConnectionStrings["itmall"].ConnectionString;

SqlConnection con = new SqlConnection(connstring);

or you can go in your way like

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["itmall"].ConnectionString);

Note:

The "name" which you gave in web.config file and name which you used in connection string must be same(like "itmall" in this solution.)