WCF打开App_messages.svclog时经常出现错误

我写了一个简单的测试Request和Response的WCF程序，运行之后打开 App_messages.svclog 时经常出现各种错误，有没有谁遇到过？错误如图所示

返回的xml文档的格式不对。

遇到尖括号等，用转义字符表示。

< and > have a special meaning in XML; they are used to define tags.
So you cannot use them elsewhere as is, you have to escape them.
< becomes <
> becomes >
& becomes &