無法從“對象”轉換為“ System.Net.Mail.MailMessage”

Question

怎么了？

我正在嘗試發送電子郵件，但問題標題中出現錯誤。 為什么不將對象轉換為“ System.Net.Mail.MailMessage”。

    private object message;

    protected void btnSend_Click(object sender, EventArgs e)
    {
        String TMess = txtMessageBody.Text;
        String TEmail = txtEmail.Text;
        String TSub = txtSubject.Text;

        //this particular email server requires us to login so
        //create a set of credentials with the relevent username and password
        System.Net.NetworkCredential userpass = new System.Net.NetworkCredential();
        userpass.UserName = "email";
        userpass.Password = "password";

        //ensure the smtp client has the newly created credentials
        client.Credentials = userpass;

        if (TSub == "")
        {
            System.Windows.Forms.MessageBox.Show("Error: Enter the message.");
        }
        else
        {
            //create a new email from REPLACE_WITH_USER@gmail.com to recipient@domain.com
            MailMessage message = new MailMessage("helloworld@gmail.com", txtEmail.Text);
        }

        //set the subject of the message, and set the body using the text from a text box
        message.Subject = txtSubject.Text;
        message.Body = txtMessageBody.Text;

        //send the message
        client.Send(message);

        //clear the message box
        //the email has been sent - either by displaying a message (e.g. a literal) or by redirecting them to a 'Message sent' page
        txtMessageBody.Text = "";
        txtEmail.Text = "";
        txtSubject.Text = "";


    }

Answer 1

var client = new SmtpClient();
var message = new MailMessage("helloworld@gmail.com", txtEmail.Text);
var subject = txtSubject.Text;
var body = txtMessageBody.Text;
message.Subject = subject;
mail.Body = body;
client.Send(message);

絕對最小值應該可以正常工作。 嘗試一次將另一條代碼添加到一行，看看它在哪里中斷。

Answer 2

問題出在您的if else循環中。 如果轉到if語句（而不是else語句），則您的mailmessage對象不存在。 不存在的內容無法解析。

 you can do it like this MailMessage message = new MailMessage("helloworld@gmail.com", txtEmail.Text if (TSub == "") { System.Windows.Forms.MessageBox.Show("Error: Enter the message."); return; }