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While setting up my new environment with a freshly deployed MongoDB container with authentication enabled, I ran into this exception: "An unhandled exception has occurred while executing the request. MongoDB.Driver.MongoConnectionException: An exception occurred while opening a connection to the server. ---> System.NotSupportedException: Unable to create an authenticator."

In my case I'm using a connection string like this example: mongodb://USER:PASSWORD@HOST:27017/?authMechanism=DEFAULT. This string works perfectly fine in MongoDB Compass but not inside my .NET 6.0 application.

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4 Answers 4

Reset to default
21

If you take a look at the source code of C# MongoDB driver in MongoCredential.cs#L469, you see this exception gets thrown while checking the auth mechanism.

After specifying the exact auth mechanism in the connection string, all exceptions are gone!

example: mongodb://USER:PASSWORD@HOST:27017/?authMechanism=SCRAM-SHA-256

Hope anyone else googeling around will find my answer helpful!

happy coding.

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9

Remove the authMechanism=DEFAULT parameter from the connection string

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This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review
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3

For me this just changed the exception to unable to authenticate using sasl protocol mechanism scram-sha-256

After some trial and error I got it working by changing the connection string to:

mongodb://USER:PASSWORD@HOST:27017/?authSource=admin

I have no idea why this was needed as the default and SCRAM-SHA-256 connectionstrings works fine in other contexts...

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1

I had similar problems and found out that usernames that include _ just don't want to work with the C# driver.

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It's very strange but it seems resolved my problem, is there any document?

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