How to add HTTP Header to SOAP Client

Question

Can someone answer me if it is possible to add HTTP header to soap client web-service calls. After surfing Internet the only thin I found was how to add SOAP header.

The code looks like this:

var client =new MyServiceSoapClient();
//client.AddHttpHeader("myCustomHeader","myValue");//There's no such method, it's just for clearness
var res = await client.MyMethod();

UPDATE:

The request should look like this
POST https://service.com/Service.asmx HTTP/1.1
Content-Type: text/xml; charset=utf-8
SOAPAction: "http://www.host.com/schemas/Authentication.xsd/Action"
Content-Length: 351
MyHeader: "myValue"
Expect: 100-continue
Accept-Encoding: gzip, deflate
Connection: Keep-Alive

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header/>
  <s:Body>
    <myBody>BodyGoesHere</myBody>
  </s:Body>
</s:Envelope>

Header property in the envelop should be empty

Answer 1

Try to use this:

SoapServiceClient client = new SoapServiceClient();

using(new OperationContextScope(client.InnerChannel)) 
{
    // // Add a SOAP Header (Header property in the envelope) to an outgoing request. 
    // MessageHeader aMessageHeader = MessageHeader
    //    .CreateHeader("MySOAPHeader", "http://tempuri.org", "MySOAPHeaderValue");
    // OperationContext.Current.OutgoingMessageHeaders.Add(aMessageHeader);

    // Add a HTTP Header to an outgoing request
    HttpRequestMessageProperty requestMessage = new HttpRequestMessageProperty();
    requestMessage.Headers["MyHttpHeader"] = "MyHttpHeaderValue";
    OperationContext.Current.OutgoingMessageProperties[HttpRequestMessageProperty.Name] 
       = requestMessage;

    var result = client.MyClientMethod();
}

See here for more detail.