Question

I want to make a database for my mobile 6 cellphone app. What I did was in visual studios I went to my project name and right clicked on it, went to add -> add new item -> data -> choose datafile.

It created a database file called “AppDatabase1.sdf”

Now I want to connect to my database but I don’t know how what the connection string is since I see no app.config where I normally would expect it to be.

So I just have

 SqlCeConnection conn = new SqlCeConnection("Not sure what to put here");
 conn.Open();

When I click on the server explorer tab I see my database so I click on it. In the properties section it has something labeled “connection string” however it looks like the path to the actual file and when I run it in the emulator I get an error.

“The database file cannot be found.
Check the path to the database.”

Thanks

Answer 1

You don’t have to create the database outside your application. It is probably better if you had a fail-safe so that if the user accidentally deletes it or it does not exist, then you can re-create it easily. This is good for initial installations. The following code will do what you want (SQLCE/Mobile 2005 example):

Private Sub ConnectToDB()
        If (File.Exists("\SystemCF\LPI\inventory.sdf")) Then
            Try
                cn = New SqlCeConnection("Data Source=\SystemCF\LPI\inventory.sdf;Password=")
                cn.Open()
            Catch ex As Exception
                MessageBox.Show(ex.Message)
            End Try

        ElseIf (File.Exists("\UserCF\LPI\inventory.sdf")) Then
            Try
                cn = New SqlCeConnection("Data Source=\UserCF\LPI\inventory.sdf;Password=")
                cn.Open()
            Catch ex As Exception
                MessageBox.Show(ex.Message)
            End Try

        Else
    Try
       If (Not (Directory.Exists("\SystemCF\LPI"))) Then
                Directory.CreateDirectory("\SystemCF\LPI")
       End If

       Dim engine As New SqlCeEngine("Data Source=\SystemCF\LPI\inventory.sdf")
       engine.CreateDatabase()

       cn = New SqlCeConnection("Data Source=\SystemCF\LPI\inventory.sdf")
       cn.Open()

       Call dropAndCreateDatabase()
     Catch ex As Exception
       MessageBox.Show(ex.Message)
       MessageBox.Show("Unable to create database!", "Database Create Failed")
     End Try
End Sub