I have encountered a strange error that is unexplainable to me. I have a .NET 6 class library project (A) that has the function:

public async Task ImportDeliveries()
{
    try
    {
        var csvFileProcessor = new CsvFileProcessor();
        await csvFileProcessor.ProcessAllAsync(_DeliveryImporter.ImportAsync).ConfigureAwait(true);
    }
    catch (Exception ex)
    {
        _TelemetryClient.TrackException(ex);
    }
}

It works fine. However, as soon as I add the project reference of another .NET 6 class library (B) to the project, without changing anything else, the function

await csvFileProcessor.ProcessAllAsync(_DeliveryImporter.ImportAsync).ConfigureAwait(true);

fails and throws the following exception:

System.MissingMethodException: 'Method not found: 'System.Threading.Tasks.Task BlobStorageHelper.BlobStorageFolder.MoveAsync(Microsoft.Azure.Storage.Blob.CloudBlockBlob, BlobStorageHelper.BlobStorageFolder)'.'

Can this be caused because (B) contains certain nuget packages? This behavior is very counterintuitive to me, and I'm not sure where to start looking.

CodePudding user response：

This is probably caused by:

• Your project, A, referencing a class library C, in which CsvFileProcessor and BlobStorageHelper.BlobStorageFolder are defined (the latter could also be in a transitive dependency, D).
• Project B also references class library C (and/or D), but a different version.
• Someone modified, added or removed System.Threading.Tasks.Task BlobStorageHelper.BlobStorageFolder.MoveAsync(Microsoft.Azure.Storage.Blob.CloudBlockBlob, BlobStorageHelper.BlobStorageFolder) in some version of C or D.
• You're not properly implementing Semantic Versioning within C or D, so MSBuild is restoring a version of C or D that doesn't contain the required method.

Hence the error.

Takeaway: changing a signature or return type is breaking the ABI (application binary interface), requiring a major version update.

To fix this, you could revert the signature or return type change, and add an overload instead.