Choose element (MSBuild)

Articol
08/25/2023

Evaluates child elements to select one set of ItemGroup elements and/or PropertyGroup elements to evaluate.

<Project> <Choose> <When> <Choose> ... <Otherwise> <Choose> ...

The Choose element contains a series of When elements with Condition attributes that are tested in order from top to bottom until one evaluates to true. If more than one When element evaluates to true, only the first one is used. An Otherwise element, if present, will be evaluated if no condition on a When element evaluates to true.

Syntax

<Choose>
    <When Condition="'StringA'=='StringB'">... </When>
    <Otherwise>... </Otherwise>
</Choose>

Attributes and elements

The following sections describe attributes, child elements, and parent elements.

Attributes

None.

Child elements

Element	Description
Otherwise	Optional element. Specifies the block of code `PropertyGroup` and `ItemGroup` elements to evaluate if the conditions of all `When` elements evaluate to `false`. There may be zero or one `Otherwise` elements in a `Choose` element, and it must be the last element.
When	Required element. Specifies a possible block of code for the `Choose` element to select. There may be one or more `When` elements in a `Choose` element.

Parent elements

Element	Description
Otherwise	Specifies the block of code to execute if the conditions of all `When` elements evaluate to `false`.
Project	Required root element of an MSBuild project file.
When	Specifies a possible block of code for the `Choose` element to select.

Remarks

The Choose, When, and Otherwise elements are used together to provide a way to select one section of code to execute out of a number of possible alternatives. For more information, see Conditional constructs.

Example

The following project uses the Choose element to select which set of property values in the When elements to set. If the Condition attributes of both When elements evaluate to false, the property values in the Otherwise element are set.

<Project
    xmlns="http://schemas.microsoft.com/developer/msbuild/2003" >
    <PropertyGroup>
        <Configuration Condition="'$(Configuration)' == ''">Debug</Configuration>
        <OutputType>Exe</OutputType>
        <RootNamespace>ConsoleApplication1</RootNamespace>
        <AssemblyName>ConsoleApplication1</AssemblyName>
        <WarningLevel>4</WarningLevel>
    </PropertyGroup>
    <Choose>
        <When Condition=" '$(Configuration)'=='debug' ">
            <PropertyGroup>
                <DebugSymbols>true</DebugSymbols>
                <DebugType>full</DebugType>
                <Optimize>false</Optimize>
                <OutputPath>.\bin\Debug\</OutputPath>
                <DefineConstants>DEBUG;TRACE</DefineConstants>
            </PropertyGroup>
            <ItemGroup>
                <Compile Include="UnitTesting\*.cs" />
                <Reference Include="NUnit.dll" />
            </ItemGroup>
        </When>
        <When Condition=" '$(Configuration)'=='retail' ">
            <PropertyGroup>
                <DebugSymbols>false</DebugSymbols>
                <Optimize>true</Optimize>
                <OutputPath>.\bin\Release\</OutputPath>
                <DefineConstants>TRACE</DefineConstants>
            </PropertyGroup>
        </When>
        <Otherwise>
            <PropertyGroup>
                <DebugSymbols>true</DebugSymbols>
                <Optimize>false</Optimize>
                <OutputPath>.\bin\$(Configuration)\</OutputPath>
                <DefineConstants>DEBUG;TRACE</DefineConstants>
            </PropertyGroup>
        </Otherwise>
    </Choose>
    <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
</Project>

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