GridView for ASP.NET Web Forms - How to specify the settings of built-in and custom command buttons based on a condition

C#
using System;
using System.Data;
using System.Web.UI.WebControls;
using DevExpress.Utils;
using DevExpress.Web;

public partial class _Default : System.Web.UI.Page {
    protected void ASPxGridView1_CommandButtonInitialize(object sender, ASPxGridViewCommandButtonEventArgs e) {
        if (e.VisibleIndex == -1) return;

        switch (e.ButtonType) {
            case ColumnCommandButtonType.Edit:
                e.Visible = EditButtonVisibleCriteria((ASPxGridView)sender, e.VisibleIndex);
                break;
            case ColumnCommandButtonType.Delete:
                e.Visible = DeleteButtonVisibleCriteria((ASPxGridView)sender, e.VisibleIndex);
                break;
        }
    }
    protected void ASPxGridView1_CustomButtonInitialize(object sender, ASPxGridViewCustomButtonEventArgs e) {
        if (e.VisibleIndex == -1) return;

        if (e.ButtonID == "btnCustom" && e.VisibleIndex % 2 != 0)
            e.Visible = DefaultBoolean.False;
    }
    protected void AccessDataSource1_Modifying(object sender, SqlDataSourceCommandEventArgs e) {
        throw new InvalidOperationException("Data modifications are not allowed in online examples");
    }
    private bool EditButtonVisibleCriteria(ASPxGridView grid, int visibleIndex) {
        object row = grid.GetRow(visibleIndex);
        return ((DataRowView)row)["ProductName"].ToString().Contains("a");
    }
    private bool DeleteButtonVisibleCriteria(ASPxGridView grid, int visibleIndex) {
        object row = grid.GetRow(visibleIndex);
        return ((DataRowView)row)["ProductName"].ToString().Contains("b");
    }
}

Visual Basic
Imports Microsoft.VisualBasic
Imports System
Imports System.Data
Imports System.Web.UI.WebControls
Imports DevExpress.Utils
Imports DevExpress.Web

Partial Public Class _Default
    Inherits System.Web.UI.Page
    Protected Sub ASPxGridView1_CommandButtonInitialize(ByVal sender As Object, ByVal e As ASPxGridViewCommandButtonEventArgs)
        If e.VisibleIndex = -1 Then
            Return
        End If

        Select Case e.ButtonType
            Case ColumnCommandButtonType.Edit
                e.Visible = EditButtonVisibleCriteria(CType(sender, ASPxGridView), e.VisibleIndex)
            Case ColumnCommandButtonType.Delete
                e.Visible = DeleteButtonVisibleCriteria(CType(sender, ASPxGridView), e.VisibleIndex)
        End Select
    End Sub
    Protected Sub ASPxGridView1_CustomButtonInitialize(ByVal sender As Object, ByVal e As ASPxGridViewCustomButtonEventArgs)
        If e.VisibleIndex = -1 Then
            Return
        End If

        If e.ButtonID = "btnCustom" AndAlso e.VisibleIndex Mod 2 <> 0 Then
            e.Visible = DefaultBoolean.False
        End If
    End Sub
    Protected Sub AccessDataSource1_Modifying(ByVal sender As Object, ByVal e As SqlDataSourceCommandEventArgs)
        Throw New InvalidOperationException("Data modifications are not allowed in online examples")
    End Sub
    Private Function EditButtonVisibleCriteria(ByVal grid As ASPxGridView, ByVal visibleIndex As Integer) As Boolean
        Dim row As Object = grid.GetRow(visibleIndex)
        Return (CType(row, DataRowView))("ProductName").ToString().Contains("a")
    End Function
    Private Function DeleteButtonVisibleCriteria(ByVal grid As ASPxGridView, ByVal visibleIndex As Integer) As Boolean
        Dim row As Object = grid.GetRow(visibleIndex)
        Return (CType(row, DataRowView))("ProductName").ToString().Contains("b")
    End Function
End Class