System.Net.Mail reference does not exist

问题

I have a problem creating application to send email.

I already have one working as a Windows Forms Application and then decided to do the same from the empty project, because I need to make a background application now.

I used the System.Net.Mail namespace for that in a Windows Forms. Then added the same code to the new project.

However, I get the following error:

The type or namespace name 'Mail' does not exist in the namespace 'System.Net'.

The 'System.Net' reference is included in the project references list and I can't find anything named 'System.Net.Mail' in the list of possible references. The point is that I didn't have those errors in Windows Forms app.

回答1:

I tried to reproduce this in Visual Studio 2012, but even when I set the compiler to use .NET 2.0 I still did not encounter this issue.

It is possible that you are missing the reference for System.dll which includes the namespace System.Net.Mail. Just as an precaution as you didn't include any sample code I will include a simple implementation of a Mail client as an example.

using (SmtpClient client = new SmtpClient("smtp-server.MyDomain.com"))
{
    client.UseDefaultCredentials = true;

    using (MailMessage mail = new MailMessage())
    {
        mail.Subject = subject;
        mail.Body = body;

        mail.From = new MailAddress("MyEmail@MyDomain.com");
        mail.To.Add("ToThisEmail@MyDomain.com");

        client.Send(mail);
    }
}

Even though I wasn't able to reproduce this I would still recommend that you verify that you are compiling your project against the same target framework as your previous client.

You can do this by right-clicking on your project and selecting Target framework under the Application tab.

Edit: It might be worth taking a screenshot of your current references and uploading it here at stackoverflow. It would give us an better overview of potential issues or conflicts.

There should be no need to modify your App.config, but as a reference here you have mine.

<?xml version="1.0"?>
<configuration>
    <startup> 
    <supportedRuntime version="v2.0.50727"/></startup>
</configuration>

Edit2:

Add the System.dll reference.

Right click on your project and choose Add Reference.
Find and add System (or System.dll) under Assemblies and Framework.
Click OK to save.

回答2:

I faced the same issue. Following changes solved my problem. Change Target framework to .Net Framework 4 from .Net Framework 4 Client Profile.

Client Profile framework creates many such issues.

来源：https://stackoverflow.com/questions/15561320/system-net-mail-reference-does-not-exist

标签

winforms

system.net.mail

system.net