Get user and password from ConnectionStringSettings
<connectionStrings>
<add name="MyConString" connectionString="Data Source=(local);Initial Catalog=MyDatabase;Persist Security Info=True;User ID=MyUsername Password=MyPassword;Connect  providerName="System.Data.SqlClient"/>
</connectionStrings>

SqlConnectionStringBuilder builder =  new SqlConnectionStringBuilder("Your connection string");
string password = builder.Password;

string connString = ConfigurationManager.ConnectionStrings["MyConString"].ConnectionString;

SqlConnectionStringBuilder con = new SqlConnectionStringBuilder(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);
string myUser = con.UserID;
string myPass = con.Password;

var builder = new SqlConnectionStringBuilder(ConfigurationManager.ConnectionStrings["MyConString"].ConnectionString)
var user = builder.UserID;
var password = builder.Password;

SqlConnectionStringBuilder yourconn = new SqlConnectionStringBuilder(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);
string password = yourconn.Password;

var connString = ConfigurationManager.ConnectionStrings["MyConString"].ConnectionString;
var tokens = connString.Split(';');

string userId;
string password;

for(var i = 0;  i < tokens.Length; i++) {
    var token = tokens[i];
    if(token.StartsWith("User ID"))
        userId = token.Substring(token.IndexOf("=") + 1);

    if(token.StartsWith("Password"))
        password = token.Substring(token.IndexOf("=") + 1);
}

string connectionString = ConfigurationManager.ConnectionStrings["MyConString"].ConnectionString;
var tokens = connectionString.Split(';').Select(n => n.Split('=');
string userId = tokens.First(n => n[0].Equals("User ID").Select(n => n[1]);
string password = tokens.First(n => n[0].Equals("Password").Select(n => n[1]);