I am encountering an issue with the latest version (2.19.0) of the MongoDB .NET driver. When performing an upsert operation using the ReplaceOneAsync method with an Expression<Func<T, bool>> filter that always returns true, the following error occurs:

MongoDB.Driver.MongoWriteException: A write operation resulted in an error. WriteError:

{ Category : "Uncategorized", Code : 224, Message : "$expr is not allowed in the query predicate for an upsert" }

.

This error was not present in the previous version (2.18.0) of the MongoDB .NET driver.

Steps to Reproduce:

> Use the latest version (2.19.0) of the MongoDB .NET driver.
> Perform an upsert operation using the ReplaceOneAsync method with an Expression<Func<T, bool>> filter that always returns true.
> Observe the error message mentioned above.

Expected Result:
The upsert operation should complete without any error, as it did in previous versions of the MongoDB .NET driver.

Actual Result:
The upsert operation fails with the error message "$expr is not allowed in the query predicate for an upsert" in MongoDB .NET driver version 2.19.0.

Environment:

MongoDB .NET driver version: 2.19.0
Platform: Windows
.NET runtime version: .NET 6

Code snippet:
// Micro-service specific code
public async Task SyncModelNameCollection(ModelName data)

{ var updatedCount = await _db.Upsert(data, ModelName.DBCollectionName, (d) => true); }

// genric library code
public async Task<long?> Upsert<T>(T data, string collectionName, Expression<Func<T, bool>> filter)
{
var options = new ReplaceOptions

{ IsUpsert = true }

;
var result = await _db.GetCollection<T>(collectionName).ReplaceOneAsync(filter, data, options);
if (result.IsModifiedCountAvailable)

{ return result.ModifiedCount; }

return null;
}