I am writting client application that uses Exchange Web Services managed API v.2.0 in order to connect to Exchange Web Services. During testing (we follow TDD) I need load EmailMessage object from saved .eml file. It’s easy find out that in order to store message object of type EmailMessage in .eml file we need call

that set MimeContent property with byte array, and then save this value in .eml file.
Now we would like to code the reverse operation. Thus we need to do the following steps:

1. Create empty EmailMessage object.
2. Load content of .eml file into MimeContent property.
3. Save EmailMessage object at Exchange server, that requires valid ExchangeService object.
4. Load primary properties of the message, and then load attachments.
5. Delete temporary message from Exchange server.

The code listed below demonstrates this workflow:

using System;
using System.IO;
using Microsoft.Exchange.WebServices.Data;

namespace Exchange.Mail
{
    public static class EmailMethods
    {
        public static EmailMessage LoadEmailMessage(ExchangeService service,
            string fileName)
        {
            // load data from file
            byte[] content;
            using (var file = File.OpenRead(fileName))
            {
                content = new byte[file.Length];
                file.Position = 0;
                file.Read(content, 0, (int)file.Length);
            }

            // create EmailMessage with mime content
            var message = new EmailMessage(service)
                 {
                     MimeContent = new MimeContent("UTF-8 ", content),
                 };
            message.Save();
            message.Load(new PropertySet(BasePropertySet.FirstClassProperties, ItemSchema.MimeContent));
            if (message.HasAttachments)
                foreach (var attachment in message.Attachments)
                    attachment.Load();
            message.Delete(DeleteMode.HardDelete);

            // set additional properties
            SetProperty(message, EmailMessageSchema.ReceivedBy, new EmailAddress("User", "User@example.com"));
            message.From = new EmailAddress("Admin", "Admin@example.com");
        }
    }
}

The code of SetProperty method is listed here.

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2. Information is provided «AS IS».