Tests the value of a property using expressions.

    <if test="${build.configuration=='release'}">
    <echo>Build release configuration</echo>
</if>

Tests the the output of a function.

    <if test="${not file::exists(filename) or file::get-length(filename) = 0}">
    <echo message="The version file ${filename} doesn't exist or is empty!" />
</if>

(Deprecated) Check that a target exists.

    <target name="myTarget" />
<if targetexists="myTarget">
    <echo message="myTarget exists" />
</if>

(Deprecated) Check existence of a property.

    <if propertyexists="myProp">
    <echo message="myProp Exists. Value='${myProp}'" />
</if>

(Deprecated) Check that a property value is true.

    <if propertytrue="myProp">
    <echo message="myProp is true. Value='${myProp}'" />
</if>

(Deprecated) Check that a property exists and is true (uses multiple conditions).

    <if propertyexists="myProp" propertytrue="myProp">
    <echo message="myProp is '${myProp}'" />
</if>

which is the same as

    <if propertyexists="myProp">
    <if propertytrue="myProp">
        <echo message="myProp is '${myProp}'" />
    </if>
</if>

(Deprecated) Check file dates. If myfile.dll is uptodate, then do stuff.

    <if uptodatefile="myfile.dll" comparefile="myfile.cs">
    <echo message="myfile.dll is newer/same-date as myfile.cs" />
</if>

or

    <if uptodatefile="myfile.dll">
    <comparefiles>
        <include name="*.cs" />
    </comparefiles>
    <echo message="myfile.dll is newer/same-date as myfile.cs" />
</if>

or

    <if>
    <uptodatefiles>
        <include name="myfile.dll" />
    </uptodatefiles>
    <comparefiles>
        <include name="*.cs" />
    </comparefiles>
    <echo message="myfile.dll is newer/same-date as myfile.cs" />
</if>

If no conditions are checked, all child tasks are executed.

If more than one attribute is used, they are &&'d. The first to fail stops the check.

The order of condition evaluation is, NAnt.Core.Tasks.IfTask.TargetNameExists, NAnt.Core.Tasks.IfTask.PropertyNameExists, NAnt.Core.Tasks.IfTask.PropertyNameTrue, NAnt.Core.Tasks.IfTask.UpToDateFile.