Set variable

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APPLIES TO: All API Management tiers

The set-variable policy declares a context variable and assigns it a value specified via an expression or a string literal. If the expression contains a literal it will be converted to a string and the type of the value will be System.String.

Note

Set a policy's elements and child elements in the order provided in the policy statement. Learn more about how to set or edit API Management policies.

Policy statement

<set-variable name="variable name" value="Expression | String literal" />

Attributes

Attribute Description Required
name The name of the variable. Policy expressions aren't allowed. Yes
value The value of the variable. This can be an expression or a literal value. Policy expressions are allowed. Yes

Usage

Allowed types

Expressions used in the set-variable policy must return one of the following basic types.

  • System.Boolean
  • System.SByte
  • System.Byte
  • System.UInt16
  • System.UInt32
  • System.UInt64
  • System.Int16
  • System.Int32
  • System.Int64
  • System.Decimal
  • System.Single
  • System.Double
  • System.Guid
  • System.String
  • System.Char
  • System.DateTime
  • System.TimeSpan
  • System.Byte?
  • System.UInt16?
  • System.UInt32?
  • System.UInt64?
  • System.Int16?
  • System.Int32?
  • System.Int64?
  • System.Decimal?
  • System.Single?
  • System.Double?
  • System.Guid?
  • System.String?
  • System.Char?
  • System.DateTime?

Example

The following example demonstrates a set-variable policy in the inbound section. This set variable policy creates an isMobile Boolean context variable that is set to true if the User-Agent request header contains the text iPad or iPhone.

<set-variable name="IsMobile" value="@(context.Request.Headers.GetValueOrDefault("User-Agent","").Contains("iPad") || context.Request.Headers.GetValueOrDefault("User-Agent","").Contains("iPhone"))" />

Next steps

For more information about working with policies, see: