An error occured at the time of creation

Dim con As New SqlConnection
        Dim dbp As String
        Dim dbSource As String
        dbp = "Data Source=.\SQLEXPRESS"
        dbSource = "Data Source=C:\Users\Administrator\Documents\mydata.mdf"

        con.ConnectionString = dbp & dbSource
        con.Open()
        MsgBox("DataBase is Now Open")
        con.Close()
        MsgBox("Database is Now Closed")

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 25 - Connection string is not valid)