How to refresh an Entity Framework Core DBContext?

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Oh, this issue had me in knots for days.

I’m using Visual Studio 2017 with .Net Core 2.1, and my EF Core code looked something like this:

//  1.  Load a [User] record from our database 
int chosenUserID = 12345;
User usr = dbContext.Users.FirstOrDefault(s => s.UserID == chosenUserID);

//  2. Call a web service, which updates that [User] record
HttpClient client = new HttpClient()
await client.PostAsync("http://someUrl", someContent);

//  3. Attempt to load an updated copy of the [User] record
User updatedUser = dbContext.Users.FirstOrDefault(s => s.UserID == chosenUserID);

At step 3, it would simply set “updatedUser” to the original version of the [User] record, rather than attempting to load in a fresh copy. So, if, after step 3, I modified that [User] record, I’d actually lose whatever settings the web service had applied to it.

I – eventually – found two solutions.

I could change the ChangeTracker settings. This worked, but I was concerned about the side-effects of doing this:

dbContext.ChangeTracker.QueryTrackingBehavior = Microsoft.EntityFrameworkCore.QueryTrackingBehavior.NoTracking;

Or, I could slip in the following command, before attempting to reload the [User] record…

await dbContext.Entry(usr).ReloadAsync();

This seems to force .Net Core to reload that [User] record, and life is good again.

I hope this is useful…

Tracking down, and fixing this bug took me days….

There’s also an excellent article describing the various ways to get around this caching issue here.

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