Property or indexer 'AnonymousType#1.FirstName' cannot be assigned to it is read only

I'm trying to make a function that changes the query result value to the values in a textbox. I can run the LINQ query, get the values, and read can print the perfectly... But when I try change the queried value to the textbox value, I get the following error:

Property or indexer 'AnonymousType#1.FirstName' cannot be assigned to -- it is read only

Here is the code:

    private void editQuery(int contactID)
    {
        ContactLINQDataContext context = new ContactLINQDataContext("Data Source=WORK-PC;Initial Catalog=Steve Harvey Team;Integrated Security=True");
        var editContact = (from Contacts in context.Contacts
                           join prop in context.Properties on Contacts.Address equals prop.PropertyID
                           join spouse in context.Contacts on Contacts.Spouse equals spouse.ContactID
                           where Contacts.ContactID == contactID
                           select new
                           {
                            ID = Contacts.ContactID,
                            FirstName = Contacts.FirstName,
                            LastName = Contacts.LastName,
                            FirstName2 = spouse.FirstName,
                            LastName2 = spouse.LastName,
                            Street = prop.Street,
                            City = prop.City,
                            State = prop.State,
                            ZIP = prop.ZIP,
                            Phone1 = Contacts.Phone,
                            Phone2 = Contacts.AltPhone,
                            Email = Contacts.Email,
                            ContactType = Contacts.Type,
                            Assets = Contacts.Assets,
                            Notes = Contacts.Notes,
                           }).First();

        editContact.FirstName = firstNameBox1.Text;

I thought it might be because I am trying to change a var type, but I don't see how I could change the type and still update the value. Any ideas?

UPDATE

I found a solution that finally worked for me. Thank you posters who replied and set me on the right track. I detailed my solution in a comment below.