假设您的requestMessage在您的其他帖子中相同(似乎是这种情况，因为错误消息表明它正在接收字符串)，因此您使用了不正确的Message.CreateMessage重载.您使用的是

Assuming your requestMessage is the same in your other post (which seems to be the case, since the error message says it's receiving a string), you're using an incorrect overload of Message.CreateMessage. The one you're using is defined as

Message.CreateMessage(MessageVersion version, string action, object body);

您传递给它的请求消息"是整个消息信封.您正在使用的这个代码将尝试序列化主体(并且由于它是字符串，因此它将序列化为< string xmlns ="http://schemas.microsoft.com/2003/10/Serialization/"> ...</string> -准确地映射到您的错误消息.

And the "request message" you're passing to it is the whole message envelope. This one you're using will try to serialize the body (and since it's a string, it will serialize it as <string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">...</string> - which maps exactly to the error message you have.

由于已经有了SOAP信封，因此需要使用的是一种重载方法，例如下面的方法:

What you need to use, since you already have the SOAP envelope, is one overload which takes that, such as the one below:

Message.CreateMessage(XmlReader enveloperReader, int maxSizeOfHeaders, MessageVersion version);

代码类似于:

string requestMessageString = @"<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
        xmlns:inf="http://www.informatica.com/"
        xmlns:wsdl="http://www.informatica.com/wsdl/">
    <soapenv:Header>
        <inf:Security>
            <UsernameToken>
                <Username>john</Username>
                <Password>jhgfsdjgfj</Password>
            </UsernameToken>
        </inf:Security>
    </soapenv:Header>
    <soapenv:Body>
        <wsdl:doClient_ws_IbankRequest>
            <wsdl:doClient_ws_IbankRequestElement>
                <!--Optional:-->
                <wsdl:Client_No>00460590</wsdl:Client_No>
            </wsdl:doClient_ws_IbankRequestElement>
        </wsdl:doClient_ws_IbankRequest>
    </soapenv:Body>
</soapenv:Envelope>";

XmlReader envelopeReader = XmlReader.Create(new StringReader(requestMessageString));
Message requestMsg = Message.CreateMessage(envelopeReader, int.MaxValue, MessageVersion.Soap11);