应用程序错误:指定的字符串不是电子邮件地址所需的格式

我想在用户点击发送按钮时向用户的帐户发送电子邮件.但我得到了上述错误.下面是我的sendClick代码.

protected void btnsendCode_Click(object sender, EventArgs e)
{
    try
    {
        if (txtemail.Text != "")
        {
            Random rd = new Random();

            veri = rd.Next(1000, 10000);
            MailMessage mm = new MailMessage();
            mm.To.Add(new MailAddress(txtemail.Text.ToString()));

            mm.From = new MailAddress("xxx@yyy.in", "Verification Mail");
            mm.Body = "Your Verification Code is - " + veri.ToString();
            mm.IsBodyHtml = true;
            mm.Subject = "Verification mail";
            SmtpClient smcl = new SmtpClient();
            smcl.Host = "smtp.gmail.com";
            smcl.Port = 587;
            smcl.Credentials = new NetworkCredential("xxx@yyy.in", "xxx");
            //smcl.EnableSsl = true;
            smcl.Send(mm);
            Page.ClientScript.RegisterStartupScript(GetType(), "msgbox", "alert('Verification Code sent to your Email ID! Please Check your Email!!');", true);
            txtverify.Enabled = true;
            btnsendCode.Text = "Send Code Again";
            lblmsg.Visible = false;
        }
        else
        {
            lblmsg.Visible = true;
            lblmsg.Text = "Please enter Email ID!!";
            lblmsg.ForeColor = System.Drawing.Color.Yellow;
            lblmsg.BorderColor = System.Drawing.Color.Red;
            lblmsg.BorderStyle = BorderStyle.Ridge;
            lblmsg.BorderWidth = new Unit("2");
            lblmsg.Focus();
        }
    }
    catch (WebException we)
    {
        lblmsg.Visible = true;
        lblmsg.Text = we.Message.ToString();
        lblmsg.ForeColor = System.Drawing.Color.Yellow;
        lblmsg.BorderColor = System.Drawing.Color.Red;
        lblmsg.BorderStyle = BorderStyle.Ridge;
        lblmsg.BorderWidth = new Unit("2");
    }
}

堆栈跟踪

[FormatException:指定的字符串不是电子邮件地址所需的格式.]
System.Net.Mail.MailAddressParser.ReadCfwsAndThrowIfIncomplete(String data,Int32 index)+1475945
System.Net.Mail.MailAddressParser.ParseDomain(String data ,Int32&index)+135 System.Net.Mail.MailAddressParser.ParseAddress(String data,Boolean expectMultipleAddresses,Int32&index)+99
System.Net.Mail.MailAddressParser.ParseAddress(String data)+23
System.Net.Mail.MailAddress. .ctor(String address,String displayName,Encoding displayNameEncoding)+220
System.Net.Mail.MailMessage..ctor()+130
events.btnsendCode_Click(Object sender,EventArgs e)在d:\ inetpub\vhosts\marpallichande.in\httpdocs\Test\events.aspx.cs:101
System.Web.UI.WebControls.Button.OnClick(EventArgs e)+9552874
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)+103
System.Web.UI .WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)+10
System.Web.UI.Page.RaisePostBac kEvent(IPostBackEventHandler sourceControl,String eventArgument)+13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)+35 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,Boolean includeStagesAfterAsyncPoint)+1724

哪个部分我犯了错误,需要纠正它？