The column 'TagId' cannot be modified because it is either a computed column or is the result of a UNION operator.

This is my table Structure,

CREATE TABLE [dbo].[Productsdata](
[ID] [int] IDENTITY(1,1) NOT NULL,
[TagId] AS ('100.1.'+CONVERT([varchar](10),[ID],(0))) PERSISTED NOT NULL,
[Name] [varchar](max) NULL,
[Address] [int] NULL,

CONSTRAINT [PrimaryKey_92b4ebad-47f3-4b86-8d04-720c8511b79e] PRIMARY KEY CLUSTERED 
(
[ID] ASC,
[TagId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
)

GO
At the time of insert new record my table Using MVC4 with Linq I am getting an error like this:

ERROR:

The column "TagId" cannot be modified because it is either a computed column or is the result of a UNION operator.
This is my code for inserting new record

 public ActionResult Createnewcar()
        {
            Productsdata p = new Productsdata();
            return View(p);
        }
       
        // POST: /Products/Create
        [HttpPost, ValidateInput(false)]
        public ActionResult Createnewcar(FormCollection collection, Productsdata p, HttpPostedFileBase[] MultipleFiles)
        {
            try
            { 
                var Tagid = collection["TagNo"];
                var qry = (from c in db.Productsdatas where c.TagId ==Tagid select c).Count();
                if (qry != 1)
                {   
                    db.Productsdatas.InsertOnSubmit(p);
                    db.SubmitChanges();
                    return RedirectToAction("Index");
                }
                else 
                { 
                    return RedirectToAction("EventCreationError");
                } 
            }
            catch
            {               
                return RedirectToAction("Createnewcar");
            }
        }
What is the mistake my code?

Give me the solution for this one