Using conditional expressions, update actions can be executed or skipped during update execution based on local state information. Using Shared Properties, you can assign a conditional expression to any update action. The action is executed based on the evaluation result of the conditional expression.

Shared Properties can be set by many of the update actions, such as the Read Registry Value action and the Read Xml Node action. Shared Properties can also set in Dynamic Actions or passed into the Update Engine from your host application.

Supported Operators

Binary
+, -, *, /, mod, >, <, >=, <=, and, &, or, |, andalso, &&, orelse, ||, xor, ^, like, =, ==, <>, !=

Unary
Not, !, ~, -

Precedence

Standard operator precedence is honored.

1. -; !, not; ~
2. . *; /; %, mod
3. +; -
4. >; <; >=; <=
5. ==, =; !=, <>; like
6. &, and
7. ^, xor
8. |, or
9. &&, andalso
10. ||, orelse

Functions

The following functions are supported in action conditional statements.

• Startswith
• Endswith
• Contains
• Substring
• Append
• Round
• Sign
• Int
• Frac

Testing Expressions in AppLife Make Update

Conditional Expressions can be tested as they are defined in AppLife Make Update. The test dialog lets you set test values for all Shared Properties contained within the expression. The expression is parsed and any syntax errors are identified at design time.

Conditional Expressions are demonstrated in the Custom Actions Quick Start project.