Erro SQL connection code with VB.net

Imports System.Data.SqlClient

Public Class Class1

    Public Shared sqlcon As New SqlConnection

End Class

Imports System.Data.SqlClient
Public Class frmLogin

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Try
            Class1.sqlcon.ConnectionString = "Data Source=TOSHIBA-PC\SQLEXPRESS;initial catalog=Employes;integrated security=true"
            MsgBox("تم الاتصال بنجاح", MsgBoxStyle.Exclamation)

        Catch ex As Exception
            MsgBox(ex.Message)

        End Try
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If txtID.Text = "" Then
            MsgBox("ادخل رقم المستخدم", MsgBoxStyle.Exclamation, "حقل إجباري")
            txtID.Focus()
            Exit Sub

        End If
        If txtpassword.Text = "" Then
            MsgBox("لابد من ادخال كلمة السر", MsgBoxStyle.Exclamation, "جقل إجباري")
            txtpassword.Focus()

            Exit Sub

        End If
        Try
            Dim str As String = "select ID,userPassword from  Users where ID='" & txtID.Text & "' and userPassword='" & txtpassword.Text & "'"
            Dim sda As New SqlDataAdapter(str, Class1.sqlcon)
            Dim ds As New DataSet
            sda.Fill(ds)
            If ds.Tables(0).Rows.Count > 0 Then
                Me.Hide()
                frmMain.Show()
            Else
                MsgBox("خطأ في البيانات المدخلة", MsgBoxStyle.Critical, "خطأ")
            End If
        Catch ex As Exception
            MsgBox(ex.Message)

        End Try
    End Sub

End class