Introduction

Yes, you can conditionally use different 32-bit and 64-bit references in Visual Studio, but the cleanest solution is usually project configuration rather than preprocessor logic in source code. The real problem is that architecture-specific assemblies or native dependencies must line up with the platform target being built.

That means the build should choose the correct reference path based on x86, x64, or sometimes AnyCPU plus native dependencies. Visual Studio and MSBuild can do this with conditional project items.

Use Separate Platform Configurations

Start by defining build configurations that clearly represent the target architecture. In many projects that means Debug|x86, Release|x86, Debug|x64, and Release|x64.

Once those configurations exist, you can attach reference paths or properties to them. That is much easier to maintain than trying to detect bitness at runtime and hoping the wrong binary still loads.

Condition References in the Project File

A common approach is to condition the Reference item in the project file on $(Platform) or $(PlatformTarget).

1<ItemGroup Condition="'$(Platform)' == 'x86'">
2  <Reference Include="Vendor.Library">
3    <HintPath>lib\x86\Vendor.Library.dll</HintPath>
4  </Reference>
5</ItemGroup>
6
7<ItemGroup Condition="'$(Platform)' == 'x64'">
8  <Reference Include="Vendor.Library">
9    <HintPath>lib\x64\Vendor.Library.dll</HintPath>
10  </Reference>
11</ItemGroup>

This tells MSBuild to include a different binary depending on the active platform configuration.

Match the Platform Target to the Dependency

The reference choice and the project platform target must agree. If you reference a 32-bit native wrapper from an AnyCPU build that later runs as 64-bit, you can still fail at load time.

For architecture-specific native dependencies, it is often safer to build explicitly for x86 or x64 instead of relying on AnyCPU.

You can inspect the build value in a target if needed:

<Target Name="ShowPlatform" BeforeTargets="Build">
  <Message Text="Platform=$(Platform), PlatformTarget=$(PlatformTarget)" Importance="high" />
</Target>

That is useful when you are not sure which property the current solution configuration is actually setting.

Prefer Packages When the Vendor Supports Them

If the dependency is distributed as a NuGet package with architecture-specific assets, use that instead of maintaining manual reference switching. Package authors can place binaries in the correct runtime-specific folders, and the build tooling can choose them automatically.

Manual conditional references are most useful when you are dealing with legacy vendor DLLs or native wrappers that are not packaged cleanly.

Keep the Solution Configuration Predictable

When several projects in one solution consume the same architecture-specific dependency, keep the platform names consistent across the whole solution. Mixed combinations such as one project using x64 and another still building AnyCPU are a common source of confusing loader errors. The build should make the architecture choice obvious at the solution level, not only inside one project file.

Common Pitfalls

• Switching the reference path but leaving the project platform target inconsistent with the binary.
• Assuming AnyCPU solves native dependency issues automatically.
• Trying to solve an assembly loading problem with C# preprocessor directives instead of build configuration.
• Editing references only in the Visual Studio UI and forgetting that the real logic lives in the project file.
• Keeping the same assembly identity in two locations without documenting which configuration selects each one.

Summary

• Visual Studio can select different 32-bit and 64-bit references during build time.
• The usual approach is conditional Reference items in the project file tied to platform configurations.
• 'x86 and x64 builds should align with the actual architecture of the dependency.'
• 'AnyCPU is not a universal answer when native binaries are involved.'
• Prefer packaged dependency management when available, and use manual conditional references for legacy cases.