.ASMX File Extension

ASP.NET Webservice Source

Developer File
The ASMX extension indicates a Microsoft Active Server Plus (ASP) file. These are source files which define Web Services called by an Active Server Page file. They are immediately compiled by ASP.NET if a request to the server is issued and can be accessed through local networks or over the Internet.

ASMX are XML based files and always start with the "@ WebService" directive which is used to correlate the URL (Uniform Resource Locator) address of the Web Service with its implementation. This is followed by the "Language" parameter which is needed to set the programming language to JScript, C# or Visual Basic.

How to open ASMX Files

Just like any XML based file, ASMX files can be opened with any text editor. They can also be opened with any major web browser and the applications below.

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Comments (1)
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Avinash Kumar
2010-04-22 22:45:57
If we were dealing with an .aspx ASP.NET web application, this design page could be used to design the user interface for the page, but since we're developing an .asmx web service that will be consumed by a machine rather than a person, this design view is not as useful to us.

If you try to add a Windows form component, you'll get an error ("Object reference not set to an instance of an object"), because the web service design view doesn't know what to do with the component.

Unlike an ASP.NET web form project, an ASP.NET web service project doesn't include the plumbing to support Windows form components