public MainWindow() { if (File.Exists("Sql.json")) { SqlDataAccess sqlDataAccess = new SqlDataAccess(); if (sqlDataAccess.Connection() == false) { InitializeComponent(); SqlViewModel sqlViewModel = new SqlViewModel(this); DataContext = sqlViewModel; } else { Welcome welcome = new Welcome(); welcome.Show(); this.Close(); } } else { InitializeComponent(); SqlViewModel sqlViewModel = new SqlViewModel(this); DataContext = sqlViewModel; } }