The property 'name' is part of the object's key information and cannot be modified. Entity Framework

I am trying to update a record and I get this error message after the context.SaveChanges();

The property 'name' is part of the object's key information and cannot be modified.

Here is the code for the update function:

 if (context.EAT_SourceNames.Any(e => e.name == newSourceName))
 {
    MessageBox.Show("Name already exists in the Database");
 }
 else
 {
    var nameToUpdate = context.EAT_SourceNames.SingleOrDefault(e => e.name == sourceName.name);
    if (nameToUpdate != null)
    {
       nameToUpdate.name = newSourceName;
       context.SaveChanges();
       RefreshDGVs();
     }
 }

My SourceNames class looks like the following:

    public EAT_SourceNames()
    {
        this.EAT_Sources = new ObservableListSource<EAT_Sources>();
    }

    public string name { get; set; }
    public string version_id { get; set; }
    public string allocation_name { get; set; }

I searched for similar questions, but could not find any working solution.

See the answer from yildizm85 to this question: entity framework not working on table without identity column

"Entity Framework requires a Primary Key to generate a model from the database. If there is no Primary Key on a table it will simply select the non-nullable columns as a concatenated primary key and the Entity will be read/only."

Looking at your EAT_SourceNames object it appears there is no primary key field so the Entity Framework is using the column 'name' as part of the composite key which means it is read-only.

The solution would be to add a Primary Key field to EAT_SourceNames and then your 'name' field would no longer be part of the primary key.

Same happened to me today. I set new entity's ID with the old record's ID and the error is gone.

//This checks whether there's a record with same specific data.
var kayitVarMi = _db.Sorgu.FirstOrDefault(a => a.Serial == sorgu.Serial);

                if (kayitVarMi != null) // If there's
                {
                    sorgu.Id = kayitVarMi.Id; //This one does the trick
                    _db.Entry(kayitVarMi).CurrentValues.SetValues(sorgu);
                }
                else // If not
                {
                    _db.Sorgu.Add(sorgu);
                }

                // This whole block is in a transaction scope so I just check recordability.
                if (_db.SaveChanges() > 0)
                {
                    _sorguKaydedildiMi = true;
                }