'Reference to type 'DependencyObject' claims it is defined in 'WindowsBase', but it could not be found' error in Visual Studio Code

Question

I'm currently trying to open a window with the System.Windows. I have included three assembly references:

<ItemGroup>
  <Reference Include="PresentationFramework">
    <HintPath>C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\PresentationFramework.dll</HintPath>
  </Reference>
  <Reference Include="WindowsBase">
    <HintPath>C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\WindowsBase.dll</HintPath>
  </Reference>
  <Reference Include="PresentationCore">
    <HintPath>C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.7.2\PresentationCore.dll</HintPath>
  </Reference>
  </ItemGroup>

Upon attempting to run it with dotnet run, I get the error, error CS7069: Reference to type 'DependencyObject' claims it is defined in 'WindowsBase', but it could not be found. I'm not sure what I'm doing wrong, since I've added an assembly reference to the needed file.

I've tried referencing the respective files in C:\Windows\Microsoft.NET\assembly, but it still didn't allow me to run the program.

Please note I am using Visual Studio Code, and not Visual Studio.

Any help is appreciated, since I'm very new to working with C# outside of a game engine.

did you install prerequisite? learn.microsoft.com/en-us/dotnet/core/tools — abolfazl sadeghi
– abolfazl sadeghi, Commented Apr 21, 2023 at 22:44

Etienne de Martel · Accepted Answer · 2023-04-22 01:24:19Z

6

So, judging by how you're trying to use dotnet run, you're using a modern version of .NET, not .NET Framework, which is the legacy version. That's good, but it does mean a few things. Those assembly references? They're for .NET Framework 4.7.2, they're not compatible with whatever .NET version you're running right now.

But that's beside the point. In modern .NET, you don't need to reference WPF assemblies by hand in your .csproj file. Since .NET 5, you only need to put <UseWPF>true</UseWPF> in a property group, and the the build tools will do the rest.

Here's an example for .NET 7:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net7.0-windows</TargetFramework> <!-- or whatever version you're using -->
    <OutputType>WinExe</OutputType> <!-- you're probably making an executable -->
    <UseWPF>true</UseWPF> <!-- this right there -->
  </PropertyGroup>

  <!-- other stuff goes here, like package references -->

</Project>

You also need to target a Windows-specific framework moniker (that's the -windows suffix in the TargetFramework), because WPF only works on Windows.

Then, you can just get rid of all those <Reference> elements. You don't need them.

edited Apr 22, 2023 at 1:24

answered Apr 22, 2023 at 1:05

Etienne de Martel

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1 Comment

Theodore Kidd Over a year ago

Thanks so much, I probably would have spent at least another 18 hours looking online for solutions.

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