Q:

EF6 - There is already an open DataReader associated with this Command which must be closed first

I am coding a MVC5 internet application and am using EF6.
I have an Edit ActionResult that is called when an Asset object is edited. I also need to update other objects values when an Asset object is edited. The UpdateAssociatedAssetObjects function does this.
I am getting the following error:
There is already an open DataReader associated with this Command which must be closed first.

In the UpdateAssociatedAssetObjects function, at the following line of code:
if (item.mapMarker.Id == asset.Id)

Here is the Edit ActionResult:
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<ActionResult> Edit(AssetViewModel assetViewModel)
{
    if (ModelState.IsValid)
    {
        db.Entry(assetViewModel.asset).State = EntityState.Modified;
        assetViewModel.asset.lastUpdate = DateTime.Now;
        if (assetViewModel.asset.linkFromExternalResource)
        {
            assetViewModel.asset.webAddress = assetViewModel.webAddress;
        }
        else
        {
            assetViewModel.asset.webAddress = assetViewModel.filename;
        }
        db.Entry(assetViewModel.asset).Property(uco => uco.creationDate).IsModified = false;
        db.Entry(assetViewModel.asset).Property(uco => uco.userName).IsModified = false;
        assetService.UpdateAssociatedAssetObjects(db, assetViewModel.asset);
        await db.SaveChangesAsync();
        return RedirectToAction("Index");
    }
    return View(assetViewModel);
}

Here is the UpdateAssociatedAssetObjects function:
public void UpdateAssociatedAssetObjects(CanFindLocationDatabaseContext db, Asset asset)
{
    foreach (var item in db.mapLocations)
    {
        if (item.mapMarker.Id == asset.Id)
        {
            item.lastUpdate = DateTime.Now;
        }
    }
}

Can I please have some help with this code?
I have tried placing the UpdateAssociatedAssetObjects function after the await db.SaveChangesAsync() and using a new database context object, but the error still occurs.
Thanks in advance

A:

In your controller method you are already opening a db connection to an entry of asset. 
In your method UpdateAssociatedAssetObjects you're trying to open a second db connection reading, while you're main is still open. Get the first object or get the list in the second object.
An alternate solution is to update the db twice.

