title: error in csproj - duplicate item
body: <p>I have error from visual studio 2010:</p>
  
  <blockquote>
    <p>Error 1   The item "CrossDomainService.svc.cs" was specified more than once in the "Sources" parameter.  Duplicate items are not supported by the "Sources" parameter.    WcfServiceDomain</p>
  </blockquote>
  
  <p>and from msbuild </p>
  
  <blockquote>
    <p>C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.CSharp.targets(160,9)
    : error MSB3105: The item "CrossDomainService.svc.cs" was specified more than o
    nce in the "Sources" parameter.  Duplicate items are not supported by the "Sources" parameter. [C:\inetpub\Wwwroot\axaptaWcfConnection\WcfServiceDomain\WcfSer
    viceDomain.csproj]</p>
  </blockquote>
  
  <p>My file is csproj:</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"&gt;
    &lt;Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" /&gt;
    &lt;PropertyGroup&gt;
      &lt;Configuration Condition=" '$(Configuration)' == '' "&gt;Debug&lt;/Configuration&gt;
      &lt;Platform Condition=" '$(Platform)' == '' "&gt;AnyCPU&lt;/Platform&gt;
      &lt;ProductVersion&gt;
      &lt;/ProductVersion&gt;
      &lt;SchemaVersion&gt;2.0&lt;/SchemaVersion&gt;
      &lt;ProjectGuid&gt;{8D40933A-E036-4CD0-9003-314A692724D5}&lt;/ProjectGuid&gt;
      &lt;ProjectTypeGuids&gt;{349c5851-65df-11da-9384-00065b846f21};{fae04ec0-301f-11d3-bf4b-00c04f79efbc}&lt;/ProjectTypeGuids&gt;
      &lt;OutputType&gt;Library&lt;/OutputType&gt;
      &lt;AppDesignerFolder&gt;Properties&lt;/AppDesignerFolder&gt;
      &lt;RootNamespace&gt;WcfServiceDomain&lt;/RootNamespace&gt;
      &lt;AssemblyName&gt;WcfServiceDomain&lt;/AssemblyName&gt;
      &lt;TargetFrameworkVersion&gt;v4.0&lt;/TargetFrameworkVersion&gt;
      &lt;TargetFrameworkProfile /&gt;
      &lt;FileUpgradeFlags&gt;
      &lt;/FileUpgradeFlags&gt;
      &lt;UpgradeBackupLocation&gt;
      &lt;/UpgradeBackupLocation&gt;
      &lt;OldToolsVersion&gt;4.0&lt;/OldToolsVersion&gt;
    &lt;/PropertyGroup&gt;
    &lt;PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' "&gt;
      &lt;DebugSymbols&gt;true&lt;/DebugSymbols&gt;
      &lt;DebugType&gt;full&lt;/DebugType&gt;
      &lt;Optimize&gt;false&lt;/Optimize&gt;
      &lt;OutputPath&gt;bin\&lt;/OutputPath&gt;
      &lt;DefineConstants&gt;DEBUG;TRACE&lt;/DefineConstants&gt;
      &lt;ErrorReport&gt;prompt&lt;/ErrorReport&gt;
      &lt;WarningLevel&gt;4&lt;/WarningLevel&gt;
      &lt;PlatformTarget&gt;x86&lt;/PlatformTarget&gt;
    &lt;/PropertyGroup&gt;
    &lt;PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' "&gt;
      &lt;DebugType&gt;pdbonly&lt;/DebugType&gt;
      &lt;Optimize&gt;true&lt;/Optimize&gt;
      &lt;OutputPath&gt;bin\&lt;/OutputPath&gt;
      &lt;DefineConstants&gt;TRACE&lt;/DefineConstants&gt;
      &lt;ErrorReport&gt;prompt&lt;/ErrorReport&gt;
      &lt;WarningLevel&gt;4&lt;/WarningLevel&gt;
    &lt;/PropertyGroup&gt;
    &lt;ItemGroup&gt;
      &lt;Reference Include="System.Web.ApplicationServices" /&gt;
      &lt;Reference Include="System.Web.DynamicData" /&gt;
      &lt;Reference Include="System.Web.Entity" /&gt;
      &lt;Reference Include="System.Configuration" /&gt;
      &lt;Reference Include="System.Drawing" /&gt;
      &lt;Reference Include="System.EnterpriseServices" /&gt;
      &lt;Reference Include="System.Runtime.Serialization" /&gt;
      &lt;Reference Include="System.ServiceModel" /&gt;
      &lt;Reference Include="System.ServiceModel.Web" /&gt;
      &lt;Reference Include="System.Web.Services" /&gt;
    &lt;/ItemGroup&gt;
    &lt;ItemGroup&gt;
      &lt;Content Include="ClientAccessPolicy.xml" /&gt;
      &lt;Content Include="CrossDomainService.svc" /&gt;
      &lt;Content Include="Service1.svc" /&gt;
      &lt;Content Include="Web.config"&gt;
        &lt;SubType&gt;Designer&lt;/SubType&gt;
      &lt;/Content&gt;
      &lt;Content Include="Web.Debug.config"&gt;
        &lt;DependentUpon&gt;Web.config&lt;/DependentUpon&gt;
      &lt;/Content&gt;
      &lt;Content Include="Web.Release.config"&gt;
        &lt;DependentUpon&gt;Web.config&lt;/DependentUpon&gt;
      &lt;/Content&gt;
    &lt;/ItemGroup&gt;
    &lt;ItemGroup&gt;
      &lt;Compile Include="CrossDomainService.svc.cs"&gt;
        &lt;DependentUpon&gt;CrossDomainService.svc&lt;/DependentUpon&gt;
      &lt;/Compile&gt;
      &lt;Compile Include="ICrossDomainService.cs" /&gt;
      &lt;Compile Include="Service1.svc.cs"&gt;
        &lt;DependentUpon&gt;Service1.svc&lt;/DependentUpon&gt;
      &lt;/Compile&gt;
      &lt;Compile Include="IService1.cs" /&gt;
      &lt;Compile Include="Properties\AssemblyInfo.cs" /&gt;
    &lt;/ItemGroup&gt;
    &lt;ProjectExtensions&gt;
      &lt;VisualStudio&gt;
        &lt;FlavorProperties GUID="{349c5851-65df-11da-9384-00065b846f21}"&gt;
          &lt;WebProjectProperties&gt;
            &lt;UseIIS&gt;False&lt;/UseIIS&gt;
            &lt;AutoAssignPort&gt;True&lt;/AutoAssignPort&gt;
            &lt;DevelopmentServerPort&gt;51421&lt;/DevelopmentServerPort&gt;
            &lt;DevelopmentServerVPath&gt;/&lt;/DevelopmentServerVPath&gt;
            &lt;IISUrl&gt;
            &lt;/IISUrl&gt;
            &lt;NTLMAuthentication&gt;False&lt;/NTLMAuthentication&gt;
            &lt;UseCustomServer&gt;False&lt;/UseCustomServer&gt;
            &lt;CustomServerUrl&gt;
            &lt;/CustomServerUrl&gt;
            &lt;SaveServerSettingsInUserFile&gt;False&lt;/SaveServerSettingsInUserFile&gt;
          &lt;/WebProjectProperties&gt;
        &lt;/FlavorProperties&gt;
      &lt;/VisualStudio&gt;
    &lt;/ProjectExtensions&gt;
    &lt;Import Project="$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v10.0\WebApplications\Microsoft.WebApplication.targets" /&gt;
  &lt;/Project&gt;
  </code></pre>
  
  <p>I not see any duplicate :/ Any idea from this error ?? </p>