UriService.cs

public class UriService : IUriService
{
    private readonly string _baseUri;

    public UriService(string baseUri)
    {
        _baseUri = baseUri;
    }

    public Uri GetPostUri(string postId)
    {
        return new Uri(_baseUri + ApiRoutes.Posts.Get.Replace("{postId}", postId));
    }

    public Uri GetAllPostsUri(PaginationQuery pagination = null)
    {
        var uri = new Uri(_baseUri);

        if (pagination == null)
        {
            return uri;
        }

        var modifiedUri = QueryHelpers.AddQueryString(_baseUri, "pageNumber", pagination.PageNumber.ToString());
        modifiedUri = QueryHelpers.AddQueryString(modifiedUri, "pageSize", pagination.PageSize.ToString());

        return new Uri(modifiedUri);
    }
}