MarketingCloud: Get the first page of records from a given Data Extension

MarketingCloudAPI.cs

using System;
using System.Text.Json.Serialization;
using System.Threading.Tasks;
using System.Linq;


using RestSharp;


public class MarketingCloudApi
{

	private readonly string _clientID = "[your client id]";
	private readonly string _clientSecret = "[your client secret]";
	private readonly string _grantType = "client_credentials";


	private readonly string _baseUri = "https://[your company id].rest.marketingcloudapis.com";
	private readonly string _baseAuth = "https://[your company id].auth.marketingcloudapis.com";

	private readonly string _endPointDataExtensionRecords = "data/v1/customobjectdata/key/{0}/rowset";


	public string AccessToken { get; set; }

	/// externalkey from your data extension
	public async Task<RestResponse> GetDataExtensionRecordsAsync(string externalKey)
	{
		AccessToken ??= await GetOAuthAccessToken();

		var _client = new RestClient(_baseUri);

		var endpoint = string.Format(_endPointDataExtensionRecords, externalKey);

		var request = new RestRequest(endpoint, Method.Get)
			.AddHeader("Authorization", "Bearer " + AccessToken);

		RestResponse response = await _client.GetAsync(request);

		// you can process the records like this
		var records = System.Text.Json.JsonSerializer.Deserialize<Rootobject>(response.Content);

		var entries = records.items.Select(x => x.values);

		return response;

		// you can also 
	}

	private async Task<string> GetOAuthAccessToken()
	{
		var _client = new RestClient(_baseAuth);

		var request = new RestRequest("v2/token", Method.Post);

		var data = new AccessTokenRequest
		{
			ClientId = _clientID,
			ClientSecret = _clientSecret,
			GrantType = _grantType
		};

		request.AddJsonBody(data);

		// Get the response.
		var response = await _client.ExecuteAsync<AccessTokenResponse>(request);

		AccessTokenResponse responseData = response.Data;

		return responseData.AccessToken;
	}
}

public partial class AccessTokenRequest
{
	[JsonPropertyName("grant_type")]
	public string GrantType { get; set; }

	[JsonPropertyName("client_id")]
	public string ClientId { get; set; }

	[JsonPropertyName("client_secret")]
	public string ClientSecret { get; set; }
}

public partial class AccessTokenResponse
{
	[JsonPropertyName("access_token")]
	public string AccessToken { get; set; }

	[JsonPropertyName("token_type")]
	public string TokenType { get; set; }

	[JsonPropertyName("expires_in")]
	public long ExpiresIn { get; set; }

	[JsonPropertyName("scope")]
	public string Scope { get; set; }

	[JsonPropertyName("soap_instance_url")]
	public string SoapInstanceUrl { get; set; }

	[JsonPropertyName("rest_instance_url")]
	public string RestInstanceUrl { get; set; }
}

public class Rootobject
{
	public Links links { get; set; }
	public string requestToken { get; set; }
	public DateTime tokenExpireDateUtc { get; set; }
	public string customObjectId { get; set; }
	public string customObjectKey { get; set; }
	public int pageSize { get; set; }
	public int page { get; set; }
	public int count { get; set; }
	public int top { get; set; }
	public Item[] items { get; set; }
}

public class Links
{
	public string self { get; set; }
}

public class Item
{
	public Keys keys { get; set; }
	public Values values { get; set; }
}

public class Keys
{
}

// the properties in the Values class will vary
// they should match the fields in your data extension
// every one will return as a string
// you will need to convert the string value to the appropriate data type when applicable
public class Values
{
	public string subscriberkey { get; set; }
	public string emailaddress { get; set; }
	public string firstname { get; set; }
	public string lastname { get; set; }
	public string mobilephone { get; set; }
	public string address { get; set; }
	public string city { get; set; }
	public string state { get; set; }
	public string zipcode { get; set; }
	public string newsoffers { get; set; }
	public string rules { get; set; }
	public string preferredchili { get; set; }
	public string entrydate { get; set; }
	public string smsoptin { get; set; }
	public string photofilename { get; set; }
}