How to use the "set-variable" Policy Statement to create custom variables for an Azure API service operation?

The "set-variable" policy statement allows you to create custom variables with given values to be used later in other policy statements.

The "set-variable" statement has the following syntax:

<set-variable name="variable_name" value="Expression | Text" /> 

If a "@(...)" expression is used, the variable have hold the objects returned from the expression in a number of C# types, like System.Boolean, System.Int32, System.Single, System.Double, System.String, System.DateTime, etc.

For example, the following inbound policy creates three variables: the first one with a text as its value; the second one with a "@(...)" expression returning a Boolean; the third one with a "@(...)" expression returning a String;

<inbound>
    <set-variable name="version" value="1.11"/>
    <set-variable name="isMobile" 
	   value="@(context.Request.Headers["User-Agent"].Contains("iPad"))"/>
    <set-variable name="method" value="@(context.Request.Method)"/>
</inbound>

For more information on "set-variable" statement, see API Management policy expressions Website.

⇒Using Azure API Policy

⇒⇒Microsoft Azure API Management Tutorials