Send mail using O365 account c#

SendMail.cs

using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Text.Json.Serialization;
using RestSharp;
public class Body
{
    [JsonPropertyName("contentType")]
    public string ContentType { get; set; }
    [JsonPropertyName("content")]
    public string Content { get; set; }
}

public class EmailAddress
{
    [JsonPropertyName("address")]
    public string Address { get; set; }
}

public class ToRecipient
{
    [JsonPropertyName("emailAddress")]
    public EmailAddress EmailAddress { get; set; }
}

public class Attachment
{
    [JsonPropertyName("@odata.type")]
    public string Type { get; set; }
    [JsonPropertyName("name")]
    public string Name { get; set; }
    [JsonPropertyName("contentType")]
    public string ContentType { get; set; }
    [JsonPropertyName("contentBytes")]
    public string ContentBytes { get; set; }
}

public class From
{
    [JsonPropertyName("emailAddress")]
    public EmailAddress EmailAddress { get; set; }
}

public class Message
{
    [JsonPropertyName("subject")]
    public string Subject { get; set; }
    [JsonPropertyName("body")]
    public Body Body { get; set; }
    [JsonPropertyName("toRecipients")]
    public List<ToRecipient> ToRecipients { get; set; }
    [JsonPropertyName("attachments")]
    public List<Attachment> Attachments { get; set; }
    [JsonPropertyName("from")]
    public From From { get; set; }
}

public class Example
{
    [JsonPropertyName("message")]
    public Message Message { get; set; }
}
class Solution
{
    static void Main(String[] args)
    {
        var payload = new Example
        {
            Message = new Message
            {
                Subject = "Send email",
                Body = new Body
                {
                    Content = "wuirbmndf",
                    ContentType = "text"
                },
                ToRecipients = new List<ToRecipient> { new ToRecipient { EmailAddress = new EmailAddress { Address = ""}} },
                From =  new From { EmailAddress = new EmailAddress { Address = "" }  },
                Attachments = new List<Attachment> 
                {
                    new Attachment 
                    {
                        Type = "#microsoft.graph.fileAttachment",
                        Name = "attachment.txt",
                        ContentType="text/plain",
                        ContentBytes="SGVsbG8gV29ybGQh"
                    }
                }
            }
        };
        var json = JsonSerializer.Serialize(payload);
        var token = @"";
        RestClient client = new RestClient();
        client.BaseUrl = new Uri(String.Format("https://graph.microsoft.com/v1.0/me/sendmail"));
        RestRequest request = new RestRequest();
        request.Method = Method.POST;
        request.AddParameter("Authorization", string.Format("Bearer " + token), ParameterType.HttpHeader);
        request.AddParameter("application/json", json, ParameterType.RequestBody);
        //request.AddHeader("ContentType", "application/json");
        //request.JsonSerializer.ContentType = "string";

        var result = client.Execute(request);

    }
}