C # serializes entities into XML with one more question mark

When debugging, the program reported the following error

The reason is that after you serialize the entity into XML in C #, there is a question mark in front of it:

The XML format is not the correct XML format, so the program error.

The solution is to add a piece of code that hides the illegal string at the beginning of the XML, as shown in the following code:

Xmlstr = System.Text.RegularExpressions.Regex.Replace (Xmlstr, "^[^<]", "");

So you put "? "Got rid of it."

C # serializes entities into XML with one more question mark