Database is not connected from webconfig file

Question

The below code is during page load event in aspx.cs file. When I load the page in chrome, it throws some error in cs file.

Stack trace error:Network related error while connecting to sql server:

protected void Page_Load(object sender, EventArgs e)
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT * FROM employee"))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.Connection = con;
                    sda.SelectCommand = cmd;
                    using (DataTable dt = new DataTable())
                    {
                        sda.Fill(dt);
                        listviewmain.DataBind();
                    }
                }
            }
        }

Connection string in web.config file:

<add name="constr"
             connectionString = "data source=.;initial catalog=[Analyst_RealEstate_WebCP];persist security info=True;user id=sa;password=pass@word1;multipleactiveresultsets=True;"
             providerName="System.Data.SqlClient"/>

Sql Connection :

When I am trying to connect in sql using these credentials, I am able to login but not through web.config file