You can create a resource group in Azure using the Azure Management Libraries in a C# Web API. Here's how I approached it. Once the method is implemented, you can create a controller to expose this functionality as an endpoint.

NuGet Package: Azure.ResourceManager (1.13.0)

/// <summary>
/// Creates a new resource group in Azure asynchronously.
/// </summary>
/// <param name="resourceGroupName">The name of the resource group to be created.</param>
/// <param name="region">The Azure region where the resource group will be created.</param>
/// <returns>A task representing the asynchronous operation of creating the resource group.</returns>
public async Task CreateResourceGroupAsync(string resourceGroupName, string region)
{
    try
    {
        // Step 1: Get an access token
        var accessToken = await _getAccessToken.GetAccessTokenAsync();

        // Step 2: Wrap the access token in a TokenCredential
        TokenCredential tokenCredential = new GetTokenCredential(accessToken);

        // Step 3: Initialize ArmClient
        ArmClient armClient = new ArmClient(tokenCredential);

        // Step 4: Define the Resource Group data
        var resourceGroupData = new ResourceGroupData(new AzureLocation(region))
        {
            Tags = { { "Environment", "Dev" } }
        };

        // Step 5: Get the subscription
        SubscriptionResource subscription = await armClient.GetSubscriptionResource(
            new ResourceIdentifier($"/subscriptions/<YOUR_SUBSCRIPTION_ID>")).GetAsync();

        // Step 6: Create or update the resource group
        ResourceGroupCollection resourceGroupCollection = subscription.GetResourceGroups();
        ArmOperation<ResourceGroupResource> operation = await resourceGroupCollection.CreateOrUpdateAsync(
            WaitUntil.Completed, resourceGroupName, resourceGroupData);

        ResourceGroupResource resourceGroup = operation.Value;

        // Log success
        Console.WriteLine($"Resource group '{resourceGroupName}' created successfully in region '{region}'.");
    }
    catch (Exception ex)
    {
        // Log error
        Console.WriteLine($"Error occurred while creating resource group '{resourceGroupName}': {ex.Message}");

        // Optionally handle specific exceptions or log events using _eventService
    }
}

Let me know if you need further clarification! You can also check out complete code solution here GitHub.