Visual Studio 2005 中vb.net 与数据库sql server2000 的连接问题

Visual Studio 2005 中 与数据库sql server2000 的连接问题
Private Sub buttonlogin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles buttonlogin.Click
        uid = txtusername.Text
        pwd = txtpassword.Text
        mydatabase = txtdb.Text
        myserver = cobserver.Text
        If db.ConnectionString <> "" Then
            MsgBox("已有用户登录，请先注销再登陆", , "登录")
            Me.Close()
            Exit Sub
        End If
        db.Connectionstring =  "workstation id="& myserver & _
                                      "user id=" & uid & _
                                      "password=" & pwd & _
                                        "Data Source=" & myserver & _
                                        "Initial Catalog=" & mydatabase

        If uid = "" Then
            MsgBox("请输入用户名", , "登录")
            Me.Close()
            Exit Sub
        End If
        On Error GoTo errorhandle
        db.Open()
        db.Close()
        With frmmain1
            .mnudatabase.Enabled = True
            .mnutrade.Enabled = True
            .mnustatistics.Enabled = True
            .mnureport.Enabled = True
            .mnudatabase.MenuItems(0).Enabled = True
            .mnudatabase.MenuItems(1).Enabled = True
            .mnudatabase.MenuItems(2).Enabled = True
            .mnudatabase.MenuItems(3).Enabled = True
            .mnudatabase.MenuItems(4).Enabled = True
            .mnudatabase.MenuItems(5).Enabled = True
            .mnudatabase.MenuItems(6).Enabled = True
            .mnudatabase.MenuItems(7).Enabled = True
        End With
        Me.Close()
        Exit Sub
errorhandle:
        showerr()
        db.C
        uid = ""
        pwd = ""
        myserver = ""
        mydatabase = ""
        Me.Close()
    End Sub
以上是我的一个程序的登陆对话框，但为什么程序就是连接不上数据库呢，急啊
求助，
是带颜色的那