Question

ExecuteNonQuery requires an open and available Connection. The connection's current state is closed.

Why always the system returns that message?

I have a sub:

Private Sub Initialization()    

    If myCEConnection.State = ConnectionState.Closed Then '--> *1
        Try
            myCEConnection.Open()
        Catch ex As Exception

        End Try
    End If

    Dim reader As SqlCeDataReader
    Dim myCommand As SqlCeCommand = myCEConnection.CreateCommand()

    myCommand.CommandText = "Command goes here"
    Try
        reader = myCommand.ExecuteReader() 
    Catch ex As Exception '--> *2

    End Try

    myCEConnection.Close()
End Sub

And I called that function from this sub:

Public myCEConnection As New SqlCeConnection("Connection String Goes Here")

Private Sub Report()
    If myCEConnection.State = ConnectionState.Closed Then '--> *1
        Try
            myCEConnection.Open()
        Catch ex As Exception

        End Try
    End If

    Initialization()

    myCEConnection.Close()
End Sub

When I try to set a breakpoint to the *1 line, the system returns myCEConnection.State = Open {1}. But when I continue to run the breakpoint, on line *2 I got: ExecuteReader requires an open and available Connection. The connection's current state is Closed.

What’s wrong with the code?

Note: Every sub/function on the class always have the If myCeConnection.State = ..... part to check the connection is already open or not. Maybe this caused the problem but I’m not quite sure.

Answer 1

You need to associate the connection and the command:

myCommand.Connection = myCEConnection

Also consider changing your code into something like this:

Dim reader As SqlCeDataReader

Using myCEConnection As New SqlCeConnection("Connection String Goes Here")
  myCEConnection.Open()
  Using myCommand As SqlCeCommand = myCEConnection.CreateCommand()
    myCommand.Connection = myCEConnection
    myCommand.CommandText = "Command goes here"
    reader = myCommand.ExecuteReader()
  End Using
End Using

You don’t really need the Try-Catch’es, and my guess is the initial myCEConnection.Open() is throwing an exception, but you never see it because of the Try-Catch.