# Commands While writing an application with MVVM, developers specify data bindings in the View Model to bind the UI and the underlying code. Sometimes it may be required that instead of simple properties, the app may have to react to commands initiated by a user that affect something in the View Model. Such commands are generally associated with button clicks of a button or Tap event of a gesture and are handled by the appropriate background handler. These Commands, that implement the ICommand interface, define the operation to be performed when the appropriate Click or Tap is performed. To use the command interface, one has to define a data binding that targets the Command Property of the Button whereas the source is a property in the ViewModel of type ICommand. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://dailyjournal.gitbook.io/notes/app-frameworks/xamarin/commands.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.