我在程序中写的发送邮件的程序，能够成功发送，但是在查看时，标题正确，邮件内容如果是中文的话就会出现“Error Reading Message or message with NULL body!! ”错误，如果内容是英文的话就显示正常。这个是什么意思啊，应该怎么解决啊 ？望各位帮忙
string name=this.TextBox1.Text;
string address=this.Textbox2.Text;
string lianxi=this.Textbox3.Text;
string xinxi=this.Textbox4.Text;
MailMessage mymail=new MailMessage();
mymail.To="收件人";
mymail.From="发件人";
mymail.Subject=name;

string items=name+address+lianxi+xinxi;
mymail.Body=items;


mymail.BodyFormat=MailFormat.Html;
mymail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1" );
mymail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", "email" );
mymail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", "password" );
mymail.Priority =MailPriority.High;

SmtpMail.SmtpServer ="www.ldate.org.cn";
SmtpMail.Send(mymail);
Response.Write("<script>alert('提交成功！');this.location='index.aspx';</script>");