Warning task

Logs a warning during a build based on an evaluated conditional statement.


The following table describes the parameters of the Warning task.

Parameter Description
Code Optional String parameter.

The warning code to associate with the warning.
File Optional String parameter.

Specifies the relevant file, if any. If no file is provided, the file containing the Warning task is used.
HelpKeyword Optional String parameter.

The Help keyword to associate with the warning. For internal use only.
HelpLink Optional String parameter.

A link to more information about the warning.
Text Optional String parameter.

The warning text that MSBuild logs if the Condition parameter evaluates to true.


The Warning task allows MSBuild projects to check for the presence of a required configuration or property before proceeding with the next build step.

If the Condition parameter of the Warning task evaluates to true, the value of the Text parameter is logged and the build continues to execute. If a Condition parameter does not exist, the warning text is logged. For more information on logging, see Obtain build logs.

In addition to the parameters listed above, this task inherits parameters from the TaskExtension class, which itself inherits from the Task class. For a list of these additional parameters and their descriptions, see TaskExtension base class.

HelpKeyword is used by Visual Studio to support the contextual help feature (F1). You can use HelpLink to associate an online help page with an error message.


The following code example checks for properties that are set on the command line. If there are no properties set, the project raises a warning event, and logs the value of the Text parameter of the Warning task.

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <Target Name="ValidateCommandLine">
            Text=" The 0 property was not set on the command line."
            Condition="'$(0)' == ''" />
            Text=" The FREEBUILD property was not set on the command line."
            Condition="'$(FREEBUILD)' == ''" />

See also