CreateImagePart overloads + implicit casts from string lead to confusion

[stephentoub]

Service

OpenAI

Describe the bug

CreateImagePart has two overloads:

public static ChatMessageContentPart CreateImagePart(BinaryData imageBytes, string imageBytesMediaType, ChatImageDetailLevel? imageDetailLevel = null);
public static ChatMessageContentPart CreateImagePart(Uri imageUri, ChatImageDetailLevel? imageDetailLevel = null);

In general for .NET APIs we try to avoid situations where the same type of argument in the same position leads to different behaviors, however here that happens because of an implicit cast from string to ChatImageDetailLevel. I had a call to CreateImagePart(imageBytes, "image/jpeg") and I then changed it to CreateImagePart(imageUrl, "image/jpeg"). It compiled fine, but then it threw an exception at run-time, because the "image/jpeg" was no longer considered to be a media type and instead considered to be an image detail level.

Steps to reproduce

See description above.

These APIs are now stable, so I'm not sure much can be done about it.

Code snippets

No response

OS

Windows 11

.NET version

.NET 8

Library version

2.0.0