Just in case someone don’t konw how to handle this.
To fix this,you need open the csproj file in your project,and navigate to
<ItemGroup>
<Reference Include="FlaxEngine.CSharp">
<HintPath>..\..\..\FlaxEngine\FlaxEditorLinux (1)\Binaries\Editor\Win64\Development\FlaxEngine.CSharp.dll</HintPath>
</Reference>
</ItemGroup>
And replace “Win64” to “Linux”, looks like below
<ItemGroup>
<Reference Include="FlaxEngine.CSharp">
<HintPath>..\..\..\FlaxEngine\FlaxEditorLinux (1)\Binaries\Editor\Linux\Development\FlaxEngine.CSharp.dll</HintPath>
</Reference>
</ItemGroup>