How to embed Image inline in Email Body using Microsoft Graph

Question

I am using a Function app to trigger a mail, using MS Graph API, the mail body text is getting triggered properly but facing issue in rendering the header and footer image shown in picture. How to solve this issue in the body level.

Below are the references of the above images in HTML/Blob file

  <img src=cid:Header.jpg>
    <img src=cid:footer.png>
    <ContentIDs>Header.jpg, footer.png</ContentIDs>

Code used in rendering the body.

             var mailContent = new Message
                {
                    Subject = em.Subject,
                    Body = new ItemBody
                    {
                        ContentType = BodyType.Html,
                        Content = m.Body,
                        ODataType = null
                    },
                    ToRecipients = toEmails,
                    CcRecipients = ccEmails,
                    ODataType = null
                };    

EDIT: Currently facing bad request in Function App after this changes. I am trying to resolve that. If you see any discrepancy in this below code feel free to comment.

            var imagePath = @"<path\Header.jpg>";
            var imageID = "Header.jpg";//file name
            byte[] imageArray = System.IO.File.ReadAllBytes(imagePath);
            var imagePath2 = @"<path\footer.png">;
            var imageID2 = "footer.png";
            byte[] imageArray2 =System.IO.File.ReadAllBytes(imagePath2);

            
            var mContent = new Message
            {
                Subject = t.Subject,//parsing from the template
                Body = new ItemBody
                {
                    ContentType = BodyType.Html,
                    Content = m.Body,
                    ODataType = "#microsoft.graph.fileAttachment"
                },
                ToRecipients = toEmails,
                CcRecipients = ccEmails,
                ODataType = "#microsoft.graph.fileAttachment",
                HasAttachments = true,
                Attachments = new MessageAttachmentsCollectionPage()
                    {
                            new FileAttachment
                        {
                                
                                ContentBytes= imageArray,
                                ContentType = "image/jpeg",
                                ContentId= imageID,
                                IsInline=true,
                                Name = "theHead",
                               
                        },
                            new FileAttachment
                            {
                                
                                ContentBytes= imageArray2,
                                ContentType = "image/png",
                                ContentId= imageID2,
                                IsInline=true,
                                Name = "thefoot",
                            }
                    }
            };

Answer 1

I write a demo for you , try the simple console app below:

using Microsoft.Graph;
using Microsoft.Graph.Auth;
using Microsoft.Identity.Client;
using System;
using System.Collections.Generic;

namespace sendEmails
{
    class Program
    {
        static void Main(string[] args)
        {
            var appID = "";
            var appSec = "";
            var tenantID = "";
            

            IConfidentialClientApplication confidentialClientApplication = ConfidentialClientApplicationBuilder
                .Create(appID)
                .WithTenantId(tenantID)
                .WithClientSecret(appSec)
                .Build();

            ClientCredentialProvider authenticationProvider = new ClientCredentialProvider(confidentialClientApplication);

            GraphServiceClient graphServiceClient = new GraphServiceClient(authenticationProvider);

            var imagePath = @"<your image path>";
            var imageID = "image1";
            

            byte[] imageArray = System.IO.File.ReadAllBytes(imagePath);

            var body = "<h1>this is superman </br> <img src='cid:"+ imageID + "'/></h1>";
            var attachments = new MessageAttachmentsCollectionPage()
            {
                new FileAttachment{
                    ContentType= "image/jpeg",
                    ContentBytes = imageArray,
                    ContentId = imageID,
                    Name= "test-image"
                }
            };
            
            var message = new Message
            {
                Subject = "TEST SENDING IMAGE ",
                Body = new ItemBody
                {
                    ContentType = BodyType.Html,
                    Content = body,
                    ODataType = null
                },
                ToRecipients = new List<Recipient>()
                {
                    new Recipient
                    {
                        EmailAddress = new EmailAddress
                        {
                            Address = "<receiver email>"
                        }
                    }
                },
                Attachments = attachments

            };
            
            graphServiceClient.Users["<user upn>"].SendMail(message, false).Request().PostAsync().GetAwaiter().GetResult();
            Console.WriteLine("ok");
        }
    }
}

Result :