Retrieving huge amount of data from WCF service in Silverlight application

Today, I was trying to figure out why my WCF service call was always throwing the generic NotFound exception when trying to retrieve large datasets. I had all the buffer limits set to 2147483647 (int.MaxValue) at Silverlight service configuration file as well as WCF service configuration section under web.config. Some more analysis revealed that I was getting a System.Net.WebException, saying: The underlying connection was closed: The connection was closed unexpectedly. After some research, I found that I need to set the maxItemsInObjectGraph for dataContractSerializer to some higher value in my web.config.

So, if you are trapped in a similar situation, here are two steps to ensure that you can retrieve large amount of data from WCF service:

1. Enable Silverlight client to retrieve huge chunks of data by enabling large buffers. You need to increase buffer and message size limits for the binding inside ServiceReferences.ClientConfig with something like:

            <binding name="BasicHttpBinding_SilverlightWCFService"
                <security mode="None" />
        <endpoint address="http://localhost:1252/SilverlightWCFService.svc"
            binding="basicHttpBinding" bindingConfiguration="BasicHttpBinding_SilverlightWCFService"
            contract="SilverlightWCFService.SilverlightWCFService" name="BasicHttpBinding_SilverlightWCFService" />

2. Enable WCF service to send large amount of data. You need to set the binding buffer limits as well as tje DataContractSerializer’s maxItemsInObjectGraph value. Here’s an extract from web.config with all the limits set to maximum:

            <!-- Create a custom binding for our service to enable sending large amount of data -->
            <binding name="MyBasicHttpBinding"
                    maxStringContentLength="2147483647" />

            <!-- Enable the serializer to serialize greater number of records -->
            <behavior name="SilverlightWCFLargeDataApplication.Web.SilverlightWCFServiceBehavior">
                <serviceMetadata httpGetEnabled="true"/>
                <serviceDebug includeExceptionDetailInFaults="false"/>
                <dataContractSerializer maxItemsInObjectGraph="2147483647"/>

    <serviceHostingEnvironment aspNetCompatibilityEnabled="false"/>
        <!-- Bind the WCF service to our custom binding -->
        <service behaviorConfiguration="SilverlightWCFLargeDataApplication.Web.SilverlightWCFServiceBehavior"
            <endpoint address="" binding="basicHttpBinding"
            <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>

That was all related to sending greater amount of data from WCF service to Silverlight application. However, if you want to send large amount of data from Silverlight to WCF service, you need one more step as you can reach the maximum permitted http request length limit (this is 4MB by default). This again can be solved by tweaking the web.config. E.g. to allow 10MB data, you need something like:

  <httpRuntime maxRequestLength="10240" />

That’s all. Let’s enjoy developing LOB applications with this great platform.