Questions about webservice

I think , If your data contains <、>、& Equisign , I'm afraid this problem will happen . Sometimes some strange white space characters can also cause this problem . I am here SQL Server Of Northwind Last work XML I have encountered such a problem when querying . Better encode the data . There are some tools on the Internet , But it seems to charge ..net I haven't found the one brought in . So I took a detour in my program , I made a toMIMEString Method , Format the string fields in the database , The code is as follows ：
private string ToMIMEString(string s)
{
StringBuilder sb = new StringBuilder();
char[] source = s.ToCharArray();
foreach(char c in source)
{
if(c=='<')
sb.Append("&lt;");
else if(c=='&')
sb.Append("&amp;");
else if(c=='>')
sb.Append("&gt;");
else if(c=='"')
sb.Append("&quot;");
else
sb.Append(c);
}
return sb.ToString();
}