Severity Code Description Project File Line Suppression State Error MSB4100 Expected "$([System.String]::Copy('%(Identity)').EndsWith('.resources.dll'))" to evaluate to a boolean instead of "$([System.String]::Copy('C:\Users\tarek\OneDrive\Desktop\StoreAp

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Answer to: MSB4100 – Expected Condition to Evaluate to Boolean

Hi,

Thank you for reporting this issue. Here’s an explanation of the problem and how you can resolve it.

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Error Summary:

You’re getting the following MSBuild error:

Error MSB4100: Expected "$([System.String]::Copy('%(Identity)').EndsWith('.resources.dll'))" to evaluate to a boolean instead of ...

This happens because the Condition attribute in your project file (or in a build target) is not evaluating to a Boolean (true/false) value as expected.

In your specific case, the condition:

!$([System.String]::Copy('%(Identity)').EndsWith('.resources.dll'))

is evaluating to a string instead of a Boolean, because MSBuild is trying to parse a literal path string that does not contain build metadata (%(Identity)) in the correct context.

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Root Cause:

%(Identity) is an item metadata, and it should only be used inside ItemGroup or Target elements where an item (e.g., @(Reference), @(Content) etc.) is being iterated.

However, in your case, the MSBuild engine is seeing a raw file path instead of a valid item, so the expression becomes invalid and fails.

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Solution:

There are two possible solutions depending on your scenario:

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Option 1: Use a Proper ItemGroup Context

Make sure that the condition using %(Identity) is inside a target that is iterating over items, for example:

<ItemGroup>

  <MyAssemblies Include="@(ReferencePath)">

    <IsNotResource>$([System.String]::Copy('%(Identity)').EndsWith('.resources.dll'))</IsNotResource>

  </MyAssemblies>

</ItemGroup>

Then later you can do:

<Message Condition="'%(MyAssemblies.IsNotResource)' == 'false'" Text="Skipping resource assembly..." />

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Option 2: Fix the Expression for a Single File Path

If you’re using a static path (like in your error message), then you don’t need metadata like %(Identity) at all. Instead, directly write:

Condition="!$([System.String]::Copy('$(MyFilePath)').EndsWith('.resources.dll'))"

Make sure $(MyFilePath) is defined earlier as a property:

<PropertyGroup>

  <MyFilePath>C:\Users\tarek\OneDrive\Desktop\StoreApi's\AllStoreApp\StoreClassLibrary\bin\Release\net8.0\StoreClassLibrary.dll</MyFilePath>

</PropertyGroup>

Now the condition will properly evaluate to true or false.

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Summary:

• The MSB4100 error happens because MSBuild expects a Boolean condition but receives a string.
• This is often caused by incorrect use of %(Identity) outside of valid MSBuild item contexts.
• Fix it by either:
  • Ensuring %(Identity) is used inside an item iteration, or
    • Replacing it with a property like $(MyFilePath) if you’re using static paths.
    • Let me know if you’d like help editing your .csproj file or inspecting the WasmApp.targets file for where the error is being triggered.

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