PRB: You Receive a "System.IO.FileNotFoundException" Error When the Client Application Calls a Web Service

When you call a Web service in a Microsoft ASP.NET Web application, you may receive the following error:

You may receive the error if one of the following conditions is true:

• The worker process does not have permissions to read to the process Temp directory, and the worker process does not have permissions to write to the process Temp directory.
  
  Note The XmlSerializer class generates and compiles code on the fly to perform serialization and deserialization. XmlSerializer uses Code Document Object Model (CodeDom) to perform the compilation. CodeDom compilation uses temporary files on a disk. If the worker process does not have the read permissions on the Temp directory and the write permissions on the Temp directory, then all calls to the Web service fail. Therefore, the worker process requires the read permissions on the Temp directory and the write permissions on the Temp directory.
  
  -or-
• There are compilation errors in the code that XmlSerializer generated.

Worker Process Account Permissions on the Temp Directory

To resolve this problem, the ASP.NET worker process account (the ASPNET account or the NETWORK SERVICE account if your application is deployed on Internet Information Services [IIS] 6.0) must have read access and write access on the Temp directory.

Note If you use impersonation, the impersonated user must have full access on the Temp directory.

To assign required permissions to the worker process account on the Temp directory, follow these steps:

1. In Microsoft Windows Explorer, locate the %windir%\temp directory.
2. Right-click %windir%\temp, and then click Properties.
3. In the Properties window, click the Security tab.
4. Click Add, type ServerName\ASPNET, and then click OK.
   
   Note Replace ServerName with the name of the Web server.
   
   Replace ASPNET with NETWORK SERVICE if you deployed your application on IIS 6.0.
5. Under Allow, click to select the Full Control check box, and then click OK.

Find Compiler Errors in the Code That XmlSerializer Generated

To find errors that are generated by the compiler, you must add a switch to the Web.config file to keep compiler-generated files. To do this, follow these steps:

1. Open the Web.config file in a text editor, such as Notepad.
2. Add an XmlSerialization.Compilation switch to the system.diagnostics section of the code, as follows:

   <configuration>
       <system.diagnostics>
            <switches>
               <add name="XmlSerialization.Compilation" value="4"/>
            </switches>
       </system.diagnostics>
   </configuration>

3. Run the client application.
   
   The client application calls the Web service.
4. Verify that the %windir%\temp directory has the _tmpname.00.cs file and the _tmpname.out file.
   
   The _tmpname.00.cs file is the generated source. The _tmpname.out file should have the compiler errors.
   
   Note Enable the read permissions and enable the write permissions to the worker process account (ASPNET or NETWORK SERVICE) to write %tmpname% files in the Temp directory.

This behavior is by design.

Steps to Reproduce the Behavior

Create a Web service

1. Start Microsoft Visual Studio .NET.
2. Create a new ASP.NET Web service project by using Microsoft Visual C# .NET or Microsoft Visual Basic .NET.
   
   By default, Service1.asmx is created.
3. Name the project WebServiceTemp.
4. In Solution Explorer, right-click Service1.asmx, and then click View Code.
5. In the Service1.asmx.cs file (or the Service1.asmx.vb file if you are using Visual Basic .NET), uncomment the default HelloWorld() WebMethod.
6. On the Build menu, click Build Solution.

Create a Client Web Application

1. Create a new ASP.NET Web application by using Visual C# .NET or Visual Basic .NET.
2. Name the project WebAppTemp.
3. In Solution Explorer, right-click References, and then click Add Web Reference.
4. In the Address text box, type the following URL for WebServiceTemp:
   
   http://localhost/WebServiceTemp/Service1.asmx
5. Click Go, and then click Add Reference.
6. Double-click WebForm1 to open the Page_Load event code.
7. Append the following code to the Page_Load event handler.
   
   Visual C# .NET Sample Code

   // Start an instance of the Web service client-side proxy.
   localhost.Service1 myProxy = new localhost.Service1();
   Response.Write( myProxy.HelloWorld());	
   

   Visual Basic .NET Sample Code

   'Start an instance of the Web service client-side proxy.
   Dim myProxy As localhost.Service1 = New localhost.Service1()
   Response.Write(myProxy.HelloWorld())
   

8. On the Build menu, click Build Solution.

Set Permissions on the Temp Directory

To assign required permissions to the worker process account on the Temp directory, follow these steps:

1. In Microsoft Windows Explorer, locate the %windir% directory.
2. Right-click %windir%\temp, and then click Properties.
3. On the Properties window, click the Security tab.
4. Click Add, type ServerName\ASPNET, and then click OK.
5. Make sure that the Write check box is not selected under Allow, and then click OK.
6. Run the Web application.
   
   You may receive the error that is mentioned in the "Symptoms" section of this article.

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base: