DBName: testDB
DBHost: USER-PCSQLEXPRESS
DBUser: testuser
DBPass: testpass

Public Shared Sub connect(DBName As String, DBHost As String, DBUser As String, DBPass As String)

    Dim builder As SqlConnectionStringBuilder = New SqlConnectionStringBuilder()
    builder.DataSource = DBHost
    builder.UserID = DBUser
    builder.Password = DBPass
    builder.InitialCatalog = DBName

    connection = New SqlConnection(builder.ConnectionString)
    connection.Open()


End Sub

Cannot open database "TestDB" requested by the login. The login failed. Login failed for user 'testuser'.