Before adding the view, check if it exists first.

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.SharePoint.Client;

namespace COM { class Program { static void Main(string[] args) { // siteURL is the string that contains the site URL string siteUrl = "http://serverName:50000/sites/Testing"; // ClientContext object is used to get the context for the SharePoint objects ClientContext clientContext = new ClientContext(siteUrl); Web web = clientContext.Web; List list = web.Lists.GetByTitle("CustomList"); ViewCollection viewColl = list.Views; clientContext.Load(viewColl, views => views.Include( view => view.Title, view => view.Id));
clientContext.ExecuteQuery(); foreach (View view in viewColl) { Console.WriteLine(view.Title + "--------" + view.Id);

        }
        Console.ReadLine();
    }
}

}

Before adding the view, check if it exists first.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.SharePoint.Client;

namespace COM
{
  class Program
  {
    static void Main(string[] args)
    {
      // siteURL is the string that contains the site URL 
      string siteUrl = "http://serverName:50000/sites/Testing";
      // ClientContext object is used to get the context for the SharePoint objects
      ClientContext clientContext = new ClientContext(siteUrl);
      Web web = clientContext.Web;
      List list = web.Lists.GetByTitle("CustomList");
      ViewCollection viewColl = list.Views;
      clientContext.Load(viewColl,
         views => views.Include(
            view => view.Title,
            view => view.Id));            
      clientContext.ExecuteQuery();
      foreach (View view in viewColl)
      {
        Console.WriteLine(view.Title + "--------" + view.Id);
      }
      Console.ReadLine();
    }
  }
}