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Choose Element (MSBuild)
Use the MSBuild Choose element to evaluate child elements and select one set of ItemGroup or PropertyGroup elements to evaluate.
08/23/2023
reference
VB
CSharp
C++
xml
<Choose> Element [MSBuild]
Choose Element [MSBuild]
ghogen
ghogen
mijacobs
msbuild

Choose element (MSBuild)

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>

See also