The free tier supports up to 5K images. There is already a NuGet package that _should_ have these methods, but here is the underlying REST Api methods: Tagged Count: https://eastus.dev.cognitive.microsoft.com/docs/services/Custom_Vision_Training_3.2/operations/5dddfe4dc8d30b100855c60d Untagged Count: https://eastus.dev.cognitive.microsoft.com/docs/services/Custom_Vision_Training_3.2/operations/5dddfe4dc8d30b100855c611