HttpContent 转换运算符

重载列表

(Byte to HttpContent)	将字节数组内容隐式转换为HttpContent对象。
(ReadOnlyMemoryByte to HttpContent)	将只读内存字节内容隐式转换为HttpContent对象。
(Stream to HttpContent)	将流内容隐式转换为HttpContent对象。
(String to HttpContent)	将字符串内容隐式转换为HttpContent对象，使用UTF-8编码。