Gridview select update,delete,insert,sorting and paging operations

Imports System.Data.SqlClient
Partial Class About
    Inherits System.Web.UI.Page
    Dim con As SqlConnection = New SqlConnection("SERVER=197.165.5.16\Sql2008;DATABASE=master;uid=sa;pwd=Sdguf;")
    Dim order As String
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        If Not IsPostBack Then
            order = "asc"
            ViewState("order") = order
            bindata()
        End If
    End Sub
    Sub bindata()
        con.Open()
        Dim da As SqlDataAdapter = New SqlDataAdapter("Select * from employee_salary", con)
        Dim ds As Data.DataSet = New Data.DataSet()
        da.Fill(ds)
        GridView1.DataSource = ds
        GridView1.DataBind()

        con.Close()
    End Sub
    Protected Sub GridView1_PageIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewPageEventArgs) Handles GridView1.PageIndexChanging
        GridView1.PageIndex = e.NewPageIndex
        bindata()
    End Sub
    Protected Sub GridView1_RowCancelingEdit(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCancelEditEventArgs) Handles GridView1.RowCancelingEdit
        GridView1.EditIndex = -1
        bindata()
    End Sub
    Protected Sub GridView1_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles GridView1.RowCommand
        If (e.CommandName.Equals("Insert")) Then
            con.Open()
            Dim com As SqlCommand = New SqlCommand("insert into employee_salary values(" + CType(GridView1.FooterRow.FindControl("TextBox4"), TextBox).Text + "," + CType(GridView1.FooterRow.FindControl("TextBox7"), TextBox).Text + "," + CType(GridView1.FooterRow.FindControl("TextBox8"), TextBox).Text + ")", con)
            com.ExecuteNonQuery()
            con.Close()
            bindata()
        End If
    End Sub
    Protected Sub GridView1_RowDeleting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewDeleteEventArgs) Handles GridView1.RowDeleting
        con.Open()
        Dim com As SqlCommand = New SqlCommand("delete from employee_salary where id=" + CType(GridView1.Rows(e.RowIndex).FindControl("Label1"), Label).Text + "", con)
        com.ExecuteNonQuery()
        con.Close()
        bindata()
    End Sub
    Protected Sub GridView1_RowEditing(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewEditEventArgs) Handles GridView1.RowEditing
        GridView1.EditIndex = e.NewEditIndex
        bindata()
    End Sub
    Protected Sub GridView1_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles GridView1.RowUpdating
        con.Open()
        Dim com As SqlCommand = New SqlCommand("update employee_salary set salary=" + CType(GridView1.Rows(e.RowIndex).FindControl("TextBox2"), TextBox).Text + ",yearofsalary=" + CType(GridView1.Rows(e.RowIndex).FindControl("TextBox3"), TextBox).Text + " where id=" + CType(GridView1.Rows(e.RowIndex).FindControl("Label4"), Label).Text + " ", con)
        com.ExecuteNonQuery()
        con.Close()
        GridView1.EditIndex = -1
        bindata()
    End Sub

    Protected Sub GridView1_SelectedIndexChanging(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSelectEventArgs) Handles GridView1.SelectedIndexChanging
        Dim row As GridViewRow = GridView1.Rows(e.NewSelectedIndex)

        ' Display the company name from the selected row.
        ' In this example, the third column (index 2) contains
        ' the company name.
        TextBox1.Text = CType(row.FindControl("Label1"), Label).Text
        TextBox5.Text = CType(row.FindControl("Label2"), Label).Text
        TextBox6.Text = CType(row.FindControl("Label3"), Label).Text

    End Sub
    Protected Sub GridView1_Sorting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewSortEventArgs) Handles GridView1.Sorting
        Try
            con.Open()
            Dim da As SqlDataAdapter = New SqlDataAdapter("Select * from employee_salary order by " + e.SortExpression.ToString() + " " + SortOrder(), con)
            Dim ds As Data.DataSet = New Data.DataSet()
            da.Fill(ds)
            GridView1.DataSource = ds
            GridView1.DataBind()
            con.Close()
            Exit Sub
        Catch ex As Exception
        End Try
    End Sub

    Public Function SortOrder() As String
        order = Convert.ToString(ViewState("order").ToString())
        If ViewState("order").ToString() = "asc" Then
            order = "desc"
            ViewState("order") = order
        ElseIf ViewState("order").ToString() = "desc" Then
            order = "asc"
            ViewState("order") = order
        End If
        Return order
    End Function

End Class