SharePoint: is user member of group function.

snippet.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.WebPartPages;

namespace Example
{
    public class ExamplePage : WebPartPage
    {

        public static bool IsMemberOfGroup(string currentUser, string groupName)
        {
            bool isMember = false;
        
            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                using(SPSite site = new SPSite(SPContext.Current.Site.ID))
                {
                    using(SPWeb web = site.OpenWeb(SPContext.Current.Web.ID))
                    {
                        try
                        {
                            SPUser user = web.SiteGroups[groupName].Users.GetByID(SPContext.Current.Web.CurrentUser.ID);
                            if(user != null)
                                isMember = true;
                        }
                        catch
                        {
                            isMember = false;
                        }
                    }
                }
            });

            return isMember;
        }
    }
}