Defines a secure, reliable and interoperable binding that is suitable for duplex service contracts or communication through SOAP intermediaries.



  <binding name="String"
    <reliableSession ordered="Boolean"
                     inactivityTimeout="TimeSpan" />
    <security mode="None/Message">
      <message clientCredentialType="None/Windows/UserName/Certificate/CardSpace"
               algorithmSuite="Basic128/Basic192/Basic256/Basic128Rsa15/Basic256Rsa15/TripleDes/TripleDesRsa15/Basic128Sha256/Basic192Sha256/TripleDesSha256/Basic128Sha256Rsa15/Basic192Sha256Rsa15/Basic256Sha256Rsa15/TripleDesSha256Rsa15" />
    <readerQuotas maxArrayLength="Integer"
                  maxStringContentLength="Integer" />

Attributes and Elements

The following sections describe attributes, child elements, and parent elements


Attribute Description
bypassProxyOnLocal A Boolean value that indicates whether to bypass the proxy server for local addresses. The default is false.
clientBaseAddress A URI that sets the base address that the client listens to for response messages from the service. If specified, this address (plus a per-channelGUID) is used for listening. If the value is not specified, the client base address is generated in a transport-specific manner. The default is null.
closeTimeout A TimeSpan value that specifies the interval of time provided for a close operation to complete. This value should be greater than or equal to Zero. The default is 00:01:00.
hostnameComparisonMode Specifies the HTTP hostname comparison mode used to parse URIs. This attribute is of type HostNameComparisonMode, which indicates whether the hostname is used to reach the service when matching on the URI. The default value is StrongWildcard, which ignores the hostname in the match.
maxBufferPoolSize An integer that specifies the maximum buffer pool size for this binding. The default is 524,288 bytes (512 * 1024). Many parts of Windows Communication Foundation (WCF) use buffers. Creating and destroying buffers each time they are used is expensive, and garbage collection for buffers is also expensive. With buffer pools, you can take a buffer from the pool, use it, and return it to the pool once you are done. Thus the overhead in creating and destroying buffers is avoided.
maxReceivedMessageSize A positive integer that specifies the maximum message size, in bytes, including headers, that can be received on a channel configured with this binding. The sender of a message exceeding this limit will receive a SOAP fault. The receiver drops the message and creates an entry of the event in the trace log. The default is 65536.
messageEncoding Defines the encoder used to encode the message. Valid values include the following:

- Text: Use a text message encoder.
- Mtom: Use a Message Transmission Organization Mechanism 1.0 (MTOM) encoder.
- The default is Text.

This attribute is of type WSMessageEncoding.
name A string that contains the configuration name of the binding. This value should be unique because it is used as an identification for the binding. Starting with .NET Framework 4, bindings and behaviors are not required to have a name. For more information about default configuration and nameless bindings and behaviors, see Simplified Configuration and Simplified Configuration for WCF Services.
openTimeout A TimeSpan value that specifies the interval of time provided for an open operation to complete. This value should be greater than or equal to Zero. The default is 00:01:00.
proxyAddress A URI that specifies the address of the HTTP proxy. If useDefaultWebProxy is true, this setting must be null. The default is null.
receiveTimeout A TimeSpan value that specifies the interval of time provided for a receive operation to complete. This value should be greater than or equal to Zero. The default is 00:01:00.
sendTimeout A TimeSpan value that specifies the interval of time provided for a send operation to complete. This value should be greater than or equal to Zero. The default is 00:01:00.
textEncoding Sets the character set encoding to be used for emitting messages on the binding. Valid values include the following:

- BigEndianUnicode: Unicode BigEndian encoding.
- Unicode: 16-bit encoding.
- UTF8: 8-bit encoding

The default is UTF8. This attribute is of type Encoding.
transactionFlow A Boolean value that specifies whether the binding supports flowing WS-Transactions. The default is false.
useDefaultWebProxy A Boolean value that indicates whether the system’s auto-configured HTTP proxy is used. The proxy address must be null (that is, not set) if this attribute is true. The default is true.

Child Elements

Element Description
<security> Defines the security settings for the binding. This element is of type WSDualHttpSecurityElement.
<readerQuotas> Defines the constraints on the complexity of SOAP messages that can be processed by endpoints configured with this binding. This element is of type XmlDictionaryReaderQuotasElement.
<reliableSession> Specifies if reliable sessions are established between channel endpoints.

Parent Elements

Element Description
<bindings> This element holds a collection of standard and custom bindings.


The WSDualHttpBinding provides the same support for Web Service protocols as the WSHttpBinding, but for use with duplex contracts. WSDualHttpBinding only supports SOAP security and requires reliable messaging. This binding requires that the client has a public URI that provides a callback endpoint for the service. This is provided by the clientBaseAddress attribute. A dual binding exposes the IP address of the client to the service. The client should use security to ensure that it only connects to services it trusts.

This binding can be used to communicate reliably through one or more SOAP intermediaries.

By default, this binding generates a runtime stack with WS-ReliableMessaging for reliability, WS-Security for message security and authentication, HTTP for message delivery, and a Text/XML message encoding.


        <binding closeTimeout="00:00:10"
          <reliableSession ordered="false"
                           inactivityTimeout="00:02:00" />
          <security mode="None">
            <message clientCredentialType="None"
                     algorithmSuite="Aes128" />

See also