User-defined project properties themselves consist of three property values:

• Name - The name of the project property. This cannot match the name of an existing help file builder project property, certain reserved MSBuild property names, or the name of an existing user-defined property.

• Condition - An optional condition that defines when the property will be evaluated and the given value used. This is useful if you have environment variables or other command-line defined properties in your build environment that do not exist on your development PC. In such cases, you can add a condition to define a default value while you test the project. For example, assume you define a property called MyCustomProperty with a value of "Test" and set the condition to '$(MyCustomProperty)' == ''. This is stored in the project file as:

  Copy

  <MyCustomProperty Condition=" '$(MyCustomProperty)' == '' ">Test</MyCustomProperty>

  The property will only be defined in the project using the given value if it does not already have a value defined elsewhere (i.e. from a command line property definition, an environment variable, etc.).

  Caution
  Entering an invalid Condition value can cause the project to become unloadable. If this occurs, you will need to edit the project file by hand with a text editor to delete the invalid property.

• Value - This defines the value to use for the property. User-defined property values are not escaped and thus can contain references to other project or MSBuild properties.

Note
The MSBuild project object does not provide a way to rename project properties. As such, if you need to rename a user-defined property, you will need to delete it and re-add it with the new name.

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