• I want to automate the creation of custom domains

• The AddCname and AddTxt Methods work correctly

• Add Subdomain gives error 400

• I am a bit lost on how to create the hostnamebinding. What values do i really need and how can i get them from azure (DomainId, ThumbprintString)?

• How do i get the verification code after creating the hostnamebinding for my TXT-Record?

public class AzureService : IAzureService
{
    private readonly ArmClient _client;
    private readonly SubscriptionResource _subscription;
    private readonly ResourceGroupResource _resourceGroup;

    public AzureService(string resourceGroupName)
    {
        _client = new ArmClient(new DefaultAzureCredential());
        _subscription = _client.GetDefaultSubscription();
        _resourceGroup = _subscription.GetResourceGroup(resourceGroupName);
    }

    public async Task AddSubdomainAsync(string appServiceName, string subdomain)
    {
        var appService = await GetAppServiceAsync(appServiceName);

        var subdomainParts = subdomain.Split('.');
        var subdomainName = string.Join('.', subdomainParts.Take(subdomainParts.Length - 2));
        var txtRecordName = $"asuid.{subdomainName}";

        var hostNameBindingData = new HostNameBindingData
        {
            SslState = HostNameBindingSslState.SniEnabled
        };

        var operation = await appService.GetSiteHostNameBindings().CreateOrUpdateAsync(WaitUntil.Completed, subdomain, hostNameBindingData);

        // Add CNAME record
        await AddCNameRecordAsync("pit-services.one", subdomainName, $"{appServiceName}.azurewebsites");

        // Add TXT record for domain verification
        await AddTxtRecordAsync("pit-services.one", txtRecordName, appService.Data.CustomDomainVerificationId);
    }

    public async Task AddCNameRecordAsync(string dnsZoneName, string recordSetName, string alias)
    {
        var dnsZone = await GetDnsZoneAsync(dnsZoneName);
        var cnameRecordSetData = new DnsCnameRecordData
        {
            TtlInSeconds = 3600,
            Cname = alias
        };

        var cnameRecordSet = await dnsZone.GetDnsCnameRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, cnameRecordSetData);
    }

    public async Task AddTxtRecordAsync(string dnsZoneName, string recordSetName, string value)
    {
        var dnsZone = await GetDnsZoneAsync(dnsZoneName);
        var txtRecordSetData = new DnsTxtRecordData
        {
            TtlInSeconds = 3600,
            DnsTxtRecords = { new DnsTxtRecordInfo { Values = { value } } }
        };

        var txtRecordSet = await dnsZone.GetDnsTxtRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, txtRecordSetData);
    }

    private async Task<DnsZoneResource> GetDnsZoneAsync(string dnsZoneName)
    {
        return await _resourceGroup.GetDnsZoneAsync(dnsZoneName);
    }

    public async Task<WebSiteResource> GetAppServiceAsync(string appServiceName)
    {
        return await _resourceGroup.GetWebSiteAsync(appServiceName);
    }
}

It works now this is my solution.

• I want to automate the creation of custom domains

• The AddCname and AddTxt Methods work correctly

• Add Subdomain gives error 400

• I am a bit lost on how to create the hostnamebinding. What values do i really need and how can i get them from azure (DomainId, ThumbprintString)?

• How do i get the verification code after creating the hostnamebinding for my TXT-Record?

public class AzureService : IAzureService
{
    private readonly ArmClient _client;
    private readonly SubscriptionResource _subscription;
    private readonly ResourceGroupResource _resourceGroup;

    public AzureService(string resourceGroupName)
    {
        _client = new ArmClient(new DefaultAzureCredential());
        _subscription = _client.GetDefaultSubscription();
        _resourceGroup = _subscription.GetResourceGroup(resourceGroupName);
    }

    public async Task AddSubdomainAsync(string appServiceName, string subdomain)
    {
        var appService = await GetAppServiceAsync(appServiceName);

        var subdomainParts = subdomain.Split('.');
        var subdomainName = string.Join('.', subdomainParts.Take(subdomainParts.Length - 2));
        var txtRecordName = $"asuid.{subdomainName}";

        var hostNameBindingData = new HostNameBindingData
        {
            SslState = HostNameBindingSslState.SniEnabled
        };

        var operation = await appService.GetSiteHostNameBindings().CreateOrUpdateAsync(WaitUntil.Completed, subdomain, hostNameBindingData);

        // Add CNAME record
        await AddCNameRecordAsync("pit-services.one", subdomainName, $"{appServiceName}.azurewebsites");

        // Add TXT record for domain verification
        await AddTxtRecordAsync("pit-services.one", txtRecordName, appService.Data.CustomDomainVerificationId);
    }

    public async Task AddCNameRecordAsync(string dnsZoneName, string recordSetName, string alias)
    {
        var dnsZone = await GetDnsZoneAsync(dnsZoneName);
        var cnameRecordSetData = new DnsCnameRecordData
        {
            TtlInSeconds = 3600,
            Cname = alias
        };

        var cnameRecordSet = await dnsZone.GetDnsCnameRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, cnameRecordSetData);
    }

    public async Task AddTxtRecordAsync(string dnsZoneName, string recordSetName, string value)
    {
        var dnsZone = await GetDnsZoneAsync(dnsZoneName);
        var txtRecordSetData = new DnsTxtRecordData
        {
            TtlInSeconds = 3600,
            DnsTxtRecords = { new DnsTxtRecordInfo { Values = { value } } }
        };

        var txtRecordSet = await dnsZone.GetDnsTxtRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, txtRecordSetData);
    }

    private async Task<DnsZoneResource> GetDnsZoneAsync(string dnsZoneName)
    {
        return await _resourceGroup.GetDnsZoneAsync(dnsZoneName);
    }

    public async Task<WebSiteResource> GetAppServiceAsync(string appServiceName)
    {
        return await _resourceGroup.GetWebSiteAsync(appServiceName);
    }
}

It works now this is my solution.

• c#
• azure
• azure-resource-manager
• azure-sdk

1 Answer 1

The code below fetches the necessary Azure resources, including the Resource Group, App Service, and DNS Zone. It also adds a subdomain with hostname binding, creates the required CNAME and TXT records for domain verification, and handles any missing verification records.

using System;
using System.Linq;
using System.Threading.Tasks;
using Azure;
using Azure.Identity;
using Azure.ResourceManager;
using Azure.ResourceManager.AppService;
using Azure.ResourceManager.AppService.Models;
using Azure.ResourceManager.Dns;
using Azure.ResourceManager.Dns.Models;
using Azure.ResourceManager.Resources;

public class AzureService
{
  private readonly ArmClient _client;
  private readonly SubscriptionResource _subscription;
  private readonly ResourceGroupResource _resourceGroup;

  public AzureService(string resourceGroupName)
  {
      _client = new ArmClient(new DefaultAzureCredential());
      _subscription = _client.GetDefaultSubscription();
      _resourceGroup = _subscription.GetResourceGroup(resourceGroupName);
  }

  public async Task AddSubdomainAsync(string appServiceName, string subdomain, string domainName)
  {
      var appService = await GetAppServiceAsync(appServiceName);

      string subdomainName = subdomain.Replace($".{domainName}", "");
      string txtRecordName = $"asuid.{subdomainName}";

      // Fetch the verification ID from App Service
      string verificationId = appService.Data.CustomDomainVerificationId;

      // Create TXT Record for domain verification
      await AddTxtRecordAsync(domainName, txtRecordName, verificationId);

      // Create the hostname binding
      var hostNameBindingData = new HostNameBindingData
      {
          SslState = HostNameBindingSslState.SniEnabled,
          HostNameType = AppServiceHostNameType.Verified,  // Fixed type
          AzureResourceType = AppServiceResourceType.Website // Fixed type
      };

      await appService.GetSiteHostNameBindings().CreateOrUpdateAsync(WaitUntil.Completed, subdomain, hostNameBindingData);

      // Add CNAME Record pointing to App Service
      await AddCNameRecordAsync(domainName, subdomainName, $"{appServiceName}.azurewebsites");
  }

  public async Task AddCNameRecordAsync(string dnsZoneName, string recordSetName, string alias)
  {
      var dnsZone = await GetDnsZoneAsync(dnsZoneName);
      var cnameRecordSetData = new DnsCnameRecordData
      {
          TtlInSeconds = 3600,
          Cname = alias
      };

      await dnsZone.GetDnsCnameRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, cnameRecordSetData);
  }

  public async Task AddTxtRecordAsync(string dnsZoneName, string recordSetName, string value)
  {
      var dnsZone = await GetDnsZoneAsync(dnsZoneName);
      var txtRecordSetData = new DnsTxtRecordData
      {
          TtlInSeconds = 3600,
          DnsTxtRecords = { new DnsTxtRecordInfo { Values = { value } } }
      };

      await dnsZone.GetDnsTxtRecords().CreateOrUpdateAsync(WaitUntil.Completed, recordSetName, txtRecordSetData);
  }

  private async Task<DnsZoneResource> GetDnsZoneAsync(string dnsZoneName)
  {
      return await _resourceGroup.GetDnsZoneAsync(dnsZoneName);
  }

  public async Task<WebSiteResource> GetAppServiceAsync(string appServiceName)
  {
      return await _resourceGroup.GetWebSiteAsync(appServiceName);
  }
}