Moderate with custom image lists in C#

Article
01/18/2024

This article provides information and code samples to help you get started using the Content Moderator SDK for .NET to:

Create a custom image list
Add and remove images from the list
Get the IDs of all images in the list
Retrieve and update list metadata
Refresh the list search index
Screen images against images in the list
Delete all images from the list
Delete the custom list

Note

There is a maximum limit of 5 image lists with each list not to exceed 10,000 images.

The console application for this guide simulates some of the tasks you can perform with the image list API.

If you don't have an Azure subscription, create a free account before you begin.

Before you can use Content Moderator services through the REST API or the SDK, you'll need an API subscription key. Subscribe to Content Moderator service in the Azure portal to obtain it.

Create your Visual Studio project

Add a new Console app (.NET Framework) project to your solution.

In the sample code, name the project ImageLists.
Select this project as the single startup project for the solution.

Install required packages

Install the following NuGet packages:

Microsoft.Azure.CognitiveServices.ContentModerator
Microsoft.Rest.ClientRuntime
Newtonsoft.Json

Update the program's using statements

Add the following using statements

using Microsoft.Azure.CognitiveServices.ContentModerator;
using Microsoft.Azure.CognitiveServices.ContentModerator.Models;
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.IO;
using System.Threading;

Create the Content Moderator client

Add the following code to create a Content Moderator client for your subscription. Update the AzureEndpoint and CMSubscriptionKey fields with the values of your endpoint URL and subscription key. You can find these in the Quick start tab of your resource in the Azure portal.

/// <summary>
/// Wraps the creation and configuration of a Content Moderator client.
/// </summary>
/// <remarks>This class library contains insecure code. If you adapt this 
/// code for use in production, use a secure method of storing and using
/// your Content Moderator subscription key.</remarks>
public static class Clients
{
	/// <summary>
	/// The base URL for Content Moderator calls.
	/// </summary>
	private static readonly string AzureEndpoint = "YOUR ENDPOINT URL";

	/// <summary>
	/// Your Content Moderator subscription key.
	/// </summary>
	private static readonly string CMSubscriptionKey = "YOUR API KEY";

	/// <summary>
	/// Returns a new Content Moderator client for your subscription.
	/// </summary>
	/// <returns>The new client.</returns>
	/// <remarks>The <see cref="ContentModeratorClient"/> is disposable.
	/// When you have finished using the client,
	/// you should dispose of it either directly or indirectly. </remarks>
	public static ContentModeratorClient NewClient()
	{
		// Create and initialize an instance of the Content Moderator API wrapper.
		ContentModeratorClient client = new ContentModeratorClient(new ApiKeyServiceClientCredentials(CMSubscriptionKey));

		client.Endpoint = AzureEndpoint;
		return client;
	}
}

Important

Remember to remove the key from your code when you're done, and never post it publicly. For production, use a secure way of storing and accessing your credentials like Azure Key Vault. See the Azure AI services security article for more information.

Initialize application-specific settings

Add the following classes and static fields to the Program class in Program.cs.

/// <summary>
/// The minimum amount of time, im milliseconds, to wait between calls
/// to the Image List API.
/// </summary>
private const int throttleRate = 3000;

/// <summary>
/// The number of minutes to delay after updating the search index before
/// performing image match operations against the list.
/// </summary>
private const double latencyDelay = 0.5;

/// <summary>
/// Define constants for the labels to apply to the image list.
/// </summary>
private class Labels
{
	public const string Sports = "Sports";
	public const string Swimsuit = "Swimsuit";
}

/// <summary>
/// Define input data for images for this sample.
/// </summary>
private class Images
{
	/// <summary>
	/// Represents a group of images that all share the same label.
	/// </summary>
	public class Data
	{
		/// <summary>
		/// The label for the images.
		/// </summary>
		public string Label;

		/// <summary>
		/// The URLs of the images.
		/// </summary>
		public string[] Urls;
	}

	/// <summary>
	/// The initial set of images to add to the list with the sports label.
	/// </summary>
	public static readonly Data Sports = new Data()
	{
		Label = Labels.Sports,
		Urls = new string[] {
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample4.png",
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample6.png",
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample9.png"
		}
	};

	/// <summary>
	/// The initial set of images to add to the list with the swimsuit label.
	/// </summary>
	/// <remarks>We're adding sample16.png (image of a puppy), to simulate
	/// an improperly added image that we will later remove from the list.
	/// Note: each image can have only one entry in a list, so sample4.png
	/// will throw an exception when we try to add it with a new label.</remarks>
	public static readonly Data Swimsuit = new Data()
	{
		Label = Labels.Swimsuit,
		Urls = new string[] {
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample1.jpg",
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample3.png",
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample4.png",
			"https://moderatorsampleimages.blob.core.windows.net/samples/sample16.png"
		}
	};

	/// <summary>
	/// The set of images to subsequently remove from the list.
	/// </summary>
	public static readonly string[] Corrections = new string[] {
		"https://moderatorsampleimages.blob.core.windows.net/samples/sample16.png"
	};
}

/// <summary>
/// The images to match against the image list.
/// </summary>
/// <remarks>Samples 1 and 4 should scan as matches; samples 5 and 16 should not.</remarks>
private static readonly string[] ImagesToScreen = new string[] {
	"https://moderatorsampleimages.blob.core.windows.net/samples/sample1.jpg",
	"https://moderatorsampleimages.blob.core.windows.net/samples/sample4.png",
	"https://moderatorsampleimages.blob.core.windows.net/samples/sample5.png",
	"https://moderatorsampleimages.blob.core.windows.net/samples/sample16.png"
};

/// <summary>
/// A dictionary that tracks the ID assigned to each image URL when 
/// the image is added to the list.
/// </summary>
/// <remarks>Indexed by URL.</remarks>
private static readonly Dictionary<string, int> ImageIdMap =
	new Dictionary<string, int>();

/// <summary>
/// The name of the file to contain the output from the list management operations.
/// </summary>
/// <remarks>Relative paths are relative to the execution directory.</remarks>
private static string OutputFile = "ListOutput.log";

/// <summary>
/// A static reference to the text writer to use for logging.
/// </summary>
private static TextWriter writer;

/// <summary>
/// A copy of the list details.
/// </summary>
/// <remarks>Used to initially create the list, and later to update the
/// list details.</remarks>
private static Body listDetails;

Note

Your Content Moderator service key has a requests-per-second (RPS) rate limit, and if you exceed the limit, the SDK throws an exception with a 429 error code. A free tier key has a one-RPS rate limit.