Login Form update query

[alexcarter404]

Hi All,
I am developing a windows form application but am struggling with running an update query when the user logs in,
I basically want the form to validate the user which it does but then i want it to update a field in the users table of an sql database.
The problem is it validates everything ok but it does not run the update query, i check the database table after i run the log in form and it does not update the logged_in field to true, it remains false.
I have
This is the code:highlighted the update query in red.

     Private Sub btnLogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLogin.Click
        Dim connection As New SqlClient.SqlConnection
        Dim command As New SqlClient.SqlCommand
        Dim adapter As New SqlClient.SqlDataAdapter
        Dim dataset As New DataSet

        connection.ConnectionString = ("Data Source=ALEX-LAPTOP\SQLEXPRESS;Initial Catalog=sldb;Integrated Security=True;Pooling=False")
        command.CommandText = "SELECT * FROM [Users] WHERE username='" & txtUsername.Text & "' AND password='" & txtPassword.Text & "';"
        connection.Open()
        command.Connection = connection
        adapter.SelectCommand = command
        adapter.Fill(dataset, "0")
        Dim count = dataset.Tables(0).Rows.Count
        If count > 0 Then
            command.CommandText = "UPDATE Users SET logged_in=True WHERE username='" & Me.txtUsername.Text & ";"
            MsgBox("Login Successful", MsgBoxStyle.Information, "Login Passed")
            currentuser = Me.txtUsername.Text
            connection.Close()
            Me.txtUsername.Clear()
            Me.txtPassword.Clear()
            Me.Hide()
            frmHome.Show()
        Else
            MsgBox("Invalid Account", MsgBoxStyle.Critical, "Login Failed")
            txtUsername.Clear()
            txtPassword.Clear()
        End If
    End Sub

Any help would be greatly appreciated, many thanks in advance!