Изменение в проекте подключения

public string connectionString = ConfigurationManager.ConnectionStrings["DM_Logger"].ConnectionString;
 
// дальше фрагмент App.config
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
    </configSections>
    <connectionStrings>
        <add name="DM_Logger" connectionString="Data Source=D:\UZ5DM\DB\HAM.mdf;Initial Catalog=Ham;Integrated Security=True"
            providerName="System.Data.SqlClient" />        
        <add name="DM_Logger.Properties.Settings.connectionString"
            connectionString="Data Source=(LocalDB)\v11.0;AttachDbFilename=D:\UZ5DM\DB\HAM.mdf;Integrated Security=True;Connect Timeout=30"
            providerName="System.Data.SqlClient" />
    </connectionStrings>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
</configuration>

string connectionString=@"Data Source = (LocalDB)\MSSQLLocalDB; AttachDbFilename = '|DataDirectory|\HAM.mdf'; Integrated Security = True";
SqlConnection sqlConnection = new SqlConnection(connectionString);
            try
            {
                sqlConnection.Open();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString(), ex.Source.ToString(), MessageBoxButtons.OK, MessageBoxIcon.Error);
                sqlConnection.Close();
            }