vb.net: Checking SQL Server status - sql-server

Question

Sometimes when my customers turn on or restart their computer, and open my vb.net application directly, the application opens before SQL Server has started completely.
This results in many unexpected behaviors. To avoid this situation, I need to start a splash screen and check the SQL Server state within it, and only when SQL Server state indicates that it is loaded completely, can I run the whole application.
The question is: how to check the SQL Server state, whether it is finished loading or not? The whole SQL Server, not the database.

Answer 1

You can instantiate a timer in your splash form that checks if it can log into the database every one second (or whatever interval you like). I'd invoke the splash form as modal so the calling app can't continue until the splash form has detected the connection and closed itself.
At the very least you need the server name to check the connection for. If it is using a named instance then the server name should also include the instance name in the format "myserver\myinstance".
I've encapsulated the connection checking logic in the 3 overloaded functions IsConnected. You can use these functions in your splash form to check connection from the timer tick. (Each depends on the next). You can use whichever function overload is suitable based on the input items you have available.
For the first overload, if the app is running under a Windows security context that can connect to the db server then you don't need to provide the username and password (pass as empty string), otherwise you need to provide those credentials needed to login to the db server. Or you can provide your own connection string or connection object for the other overloads.
(code within the splash form)...
Private Sub Timer1_Tick(sender As Object, e As System.EventArgs) Handles Timer1.Tick
If Me.IsConnected("(local)\SQL2008R2", "", "") Then Me.Close()
End Sub
Public Function IsConnected(ServerName As String, UserID As String, Password As String) As Boolean
Dim connStr As String = String.Format("Data Source={0}", ServerName)
If Not String.IsNullOrEmpty(UserID) Then
connStr &= String.Format(";User ID={0};Password={1}", UserID, Password)
Else
connStr &= ";Integrated Security=True"
End If
Return IsConnected(connStr)
End Function
Public Function IsConnected(Connection As String) As Boolean
Static conn As SqlConnection
If conn Is Nothing Then
conn = New SqlConnection(Connection)
conn.Open()
End If
Return IsConnected(conn)
End Function
Public Function IsConnected(ByRef Conn As SqlConnection) As Boolean
If Conn IsNot Nothing Then Return (Conn.State = ConnectionState.Open)
Return False
End Function
I'd invoke the splash form from the main app as a modal dialog, as such, so the app is blocked until the connection is detected.
(from the calling app form...)
frm_Splash.ShowDialog()