使用数据阅读器选择和显示数据的问题

Question

I've been practicing and playing around with codes in VB.NET and ASP.NET. I have a program where I have a GridView name gvPerson. In the GridView, there is a list of Personnel with their details such as Name, Badge Number, Hire Date, etc. On top of the GridView, I have link button controls: Add Staff, Issue Staff Equipment, Edit Staff, and Delete Staff. So for example, when I select someone from the gridview and then click Issue staff equipment, the selected person's name and ID will by on the modal form that appears. My problem now is when I run my code, I'm getting an error which states that I don't have anything in my DataAdapter. Being kinda new to this, I believe my logic is a bit off and I may have missed something. Here's what I have:

Dim strSelectedPersonID As String
Dim strSelectedPersonName As String
Dim strSelectPosition As String
Dim strBadgeNo As String

If e.CommandName = "Select" Then
    idx = Convert.ToInt32(e.CommandArgument)

    Dim row As GridViewRow = gvPerson.Rows(idx)

    strSelectedPersonID = row.Cells(1).Text

    Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("ConnectionString2").ToString())
        conn.Open()
        Dim dsPerson As New DataSet()
        Dim dr As SqlDataReader
        Dim da As SqlDataAdapter

        Dim strSelectCmd As String = "SELECT * FROM Personnel WHERE SempID = @SempID "
        Dim cmd As New SqlCommand(strSelectCmd, conn)

        cmd.Parameters.AddWithValue("@SempID", strSelectedPersonID)
        cmd.Connection = conn
        da.SelectCommand = cmd
        dr = cmd.ExecuteReader()

        If dr.HasRows Then

            While (dr.Read())
                strSelectPosition = dr(3).ToString
                strBadgeNo = dr(4).ToString
            End While

        End If


        strSelectedPersonName = cmd.ExecuteScalar()
        tbEditPosition.Text = strSelectPosition
        tbEditBadge.Text = strBadgeNo
        conn.Close()

    End Using

End If

tbSecID.Text = strSelectedPersonID
tbSecName.Text = strSelectedPersonName

EDIT: Here's the code I where I used DataAdapter:

Try
        strconn.Open()

        Dim sQuery As String = "SELECT * FROM tblUsers WHERE Username = @Username AND Password = @Password AND Status= @Status"

        Dim datareader As SqlDataReader
        Dim adapter As New SqlDataAdapter
        Dim parameter As New SqlParameter
        Dim command As SqlCommand = New SqlCommand(sQuery, strconn)

        command.Parameters.AddWithValue("@Username", txtUsername.Text)
        command.Parameters.AddWithValue("@Password", txtPassword.Text)
        command.Parameters.AddWithValue("@Status", 1)

        command.Connection = strconn
        adapter.SelectCommand = command
        datareader = command.ExecuteReader()

        If datareader.HasRows Then

            While (datareader.Read())
                strUserID = datareader(0).ToString
                strUserFname = datareader(3).ToString
                strUserLname = datareader(4).ToString
            End While

            xPersonID = strUserID
            xPersonName = strUserFname + " " + strUserLname

            'MsgBox("Login Successfull!     ", vbInformation, vbOKOnly)

            Response.Redirect("http://localhost:00000/index.aspx")
            datareader.Close()
            LoginOk = True

        Else
            Response.Write("<SCRIPT LANGUAGE=""JavaScript"">  alert('Invalid Username or Password!');</script>")
            ' MsgBox("Invalid Username or Password!    ", vbInformation, vbOKOnly)
            txtUsername.Text = ""
            txtPassword.Text = ""
            txtUsername.Focus()
        End If
        datareader.Close()

    Catch ex As Exception
        'MsgBox(ex.Message)
    End Try

Answer 1

Thanks everyone for your input. I used SqlDataReader to go through the table and select the user's details. Everything seems to be working fine now. Here's what I came up with:

    Dim strSelectedPersonID As String
    Dim strSelectedPersonName As String
    Dim strSelectPosition As String
    Dim strBadgeNo As String
    Dim strDateHired As String
    Dim strContactNo As String
    Dim strEmail As String
    Dim strEmerContactNo As String
    Dim strContactPerson As String
    Dim strRemarks As String

    If e.CommandName = "Select" Then
        idx = Convert.ToInt32(e.CommandArgument)

        Dim row As GridViewRow = gvPerson.Rows(idx)

        strSelectedPersonID = row.Cells(1).Text

        Using conn As New SqlConnection(ConfigurationManager.ConnectionStrings("ConnectionString2").ToString())
            conn.Open()
            Dim dsPerson As New DataSet()
            Dim dr As SqlDataReader

            Dim strSelectCmd As String = "SELECT * FROM Personnel WHERE SempID = @SempID "
            Dim cmd As New SqlCommand(strSelectCmd, conn)

            cmd.Parameters.AddWithValue("@SempID", strSelectedPersonID)
            cmd.Connection = conn
            dr = cmd.ExecuteReader()

            If dr.HasRows Then

                While (dr.Read())
                    strSelectedPersonName = dr(1).ToString
                    strSelectPosition = dr(2).ToString
                    strBadgeNo = dr(3).ToString
                    strDateHired = dr(4).ToString
                    strContactNo = dr(5).ToString
                    strEmail = dr(6).ToString
                    strEmerContactNo = dr(7).ToString
                    strContactPerson = dr(8).ToString
                    strRemarks = dr(10).ToString
                End While

            End If


            'strSelectedPersonName = cmd.ExecuteScalar()
            tbSecName.Text = strSelectedPersonName
            tbEditPosition.Text = strSelectPosition
            tbEditBadge.Text = strBadgeNo
            tbEditHireDate.Text = strDateHired
            tbEditContactNo.Text = strContactNo
            tbEditEmail.Text = strEmail
            tbEmerNo.Text = strEmerContactNo
            tbEditContactPerson.Text = strContactPerson
            tbEditRemarks.Text = strRemarks
            conn.Close()

        End Using

    End If

    tbEditName.Text = strSelectedPersonName
    tbSecID.Text = strSelectedPersonID
    tbSecName.Text = strSelectedPersonName