NullReferenceException was unhandled

Question

I have the following form

 Imports System.Data.SqlClient
Public Class Main
    Protected WithEvents DataGridView1 As DataGridView
    Dim instForm2 As New Exceptions
    Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles startpayrollButton.Click
        Dim ssql As String = "select MAX(payrolldate) AS [payrolldate], " & _
                 "dateadd(s,  518399, max(payrolldate)) AS [Sunday]" & _
                  "from dbo.payroll" & _
                  " where payrollran = 'no'"
        Dim oCmd As System.Data.SqlClient.SqlCommand
        Dim oDr As System.Data.SqlClient.SqlDataReader
        oCmd = New System.Data.SqlClient.SqlCommand
 
        Try
            With oCmd
                .Connection = New System.Data.SqlClient.SqlConnection("Initial Catalog=mdr;Data Source=xxxxx;uid=xxxxx;password=xxxxx")
                .Connection.Open()
                .CommandType = CommandType.Text
                .CommandText = ssql
                oDr = .ExecuteReader()
            End With
            If oDr.Read Then
                payperiodstartdate = oDr.GetDateTime(1)
                payperiodenddate = payperiodstartdate.AddDays(7)
                Dim ButtonDialogResult As DialogResult
                ButtonDialogResult = MessageBox.Show("      The Next Payroll Start Date is: " & payperiodstartdate.ToString() & System.Environment.NewLine & "            Through End Date: " & payperiodenddate.ToString())
                If ButtonDialogResult = Windows.Forms.DialogResult.OK Then
                    exceptionsButton.Enabled = True
                    startpayrollButton.Enabled = False
                End If
            End If
            oDr.Close()
            oCmd.Connection.Close()
        Catch ex As Exception
            MessageBox.Show(ex.Message)
            oCmd.Connection.Close()
        End Try
 
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles exceptionsButton.Click
        Dim connection As System.Data.SqlClient.SqlConnection
        Dim connectionString As String = "Initial Catalog=mdr;Data Source=xxxxx;uid=xxxxx;password=xxxxx"
        Dim ds As New DataSet
        Dim _sql As String = "SELECT [Exceptions].Employeenumber,[Exceptions].exceptiondate, [Exceptions].starttime, [exceptions].endtime, [Exceptions].code, datediff(minute, starttime, endtime)  as duration INTO scratchpad3" & _
 " FROM Employees INNER JOIN Exceptions ON [Exceptions].EmployeeNumber = [Exceptions].Employeenumber" & _
 " where [Exceptions].exceptiondate between @payperiodstartdate and @payperiodenddate" & _
 " GROUP BY [Exceptions].Employeenumber, [Exceptions].Exceptiondate, [Exceptions].starttime, [exceptions].endtime," & _
 " [Exceptions].code, [Exceptions].exceptiondate"
        connection = New SqlConnection(connectionString)
        Dim _CMD As SqlCommand = New SqlCommand(_sql, connection)
        Dim adapter As System.Data.SqlClient.SqlDataAdapter
        adapter.SelectCommand = _CMD
        _CMD.Parameters.Add(New SqlClient.SqlParameter("@payperiodstartdate", payperiodstartdate))
        _CMD.Parameters.Add(New SqlClient.SqlParameter("@payperiodenddate", payperiodenddate))
        Try
            adapter.Fill(ds)
            If (ds Is Nothing) Then
                'it's empty
                MsgBox("There was no data for this time period, press Ok to continue", "No Data")
                connection.Close()
                Exceptions.Hide()
            Else
                'it exists and there are rows 
                adapter.Fill(ds)
                connection.Close()
            End If
 
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
            connection.Close()
        End Try
        Exceptions.Show()
    End Sub
    Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
 
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
End Class
 

and when I run this with debug, I get to this line

  adapter.SelectCommand = _CMD

and get the error of NullReferenceException was unhandled. Intellisense warns me that the variable adapter is used before it has been assigned a value. I've tried 

  Dim adapter As System.Data.SqlClient.SqlDataAdapter = Nothing

can anyone offer some assitance on this?

Thank you

Doug