There's an old problem in generated WCF clients in which the <c>Dispose()</c> method calls <c>Close()</c> on the client irrespective of whether there was a fault. If there was a fault, then the method should call <c>Abort()</c> instead. Failure to do so causes another exception, which masks the original exception. Client code will see the subsequent fault rather than the original one. A developer running the code in debug mode will have be misled as to what really happened. You can see <a href="http://geekswithblogs.net/DavidBarrett/archive/2007/11/22/117058.aspx" author="David Barrett" source="">WCF Clients and the "Broken" IDisposable Implementation</a> for a more in-depth analysis, but that's the gist of it. This issue is still present in the <c>ClientBase</c> implementation in .NET 4.5.1. The linked article shows how you can add your own implementation of the <c>Dispose()</c> method in each generated client. An alternative is to use a generic adaptor if you don't feel like adding a custom dispose to every client you create.<fn> <code> <b>public class</b> SafeClient<t> : IDisposable <b>where</b> T : ICommunicationObject, IDisposable { <b>public</b> SafeClient(T client) { <b>if</b> (client == <b>null</b>) { <b>throw new</b> ArgumentNullException("client"); } Client = client; } <b>public</b> T Client { <b>get</b>; <b>private set</b>; } <b>public void</b> Dispose() { Dispose(<b>true</b>); GC.SuppressFinalize(<b>this</b>); } <b>protected virtual void</b> Dispose(<b>bool</b> disposing) { <b>if</b> (disposing) { <b>if</b> (Client != <b>null</b>) { <b>if</b> (Client.State == CommunicationState.Faulted) { Client.Abort(); } <b>else</b> { Client.Close(); } Client = <b>default</b>(T); } } } } </code> To use your WCF client safely, you wrap it in the class defined above, as shown below. <code> <b>using</b> (<b>var</b> safeClient = <b>new</b> SafeClient<systemloginserviceclient>(<b>new</b> SystemLoginServiceClient(...))) { <b>var</b> client = safeClient.Client; // Work with "client" } </code> If you can figure out how to initialize your clients without passing parameters to the constructor, you could slim it down by adding a "new" generic constraint to the parameter T in <c>SafeClient</c> and then using the <c>SafeClient</c> as follows: <code> <b>using</b> (<b>var</b> safeClient = <b>new</b> SafeClient<systemloginserviceclient>()) { <b>var</b> client = safeClient.Client; // Work with "client" } </code> <hr> <ft>The code included in this article is a sketch of a solution and has not been tested. It does compile, though.</ft>