dotnet-core/release-notes/3.0/preview/3.0.0-preview-known-issues.md

# .NET Core 3.0 Preview Known Issues

This document lists known issues for **.NET Core 3.0 Preview releases** which may be encountered during usage.


## ASP.NET Core

### Preview 3

- **Updates to .razor files fail to show up in subsequent builds**: Updates to Razor Component (.razor) in Visual Studio may fail to show up in subsequent builds. To work around this issue add the following item group to the project file:

    ```xml
    <ItemGroup>
        <UpToDateCheckInput Include="@(Content->WithMetadataValue('Extension', '.razor'))" />
    </ItemGroup>
    ```

- **Updates to Razor Components in .razor files fail to show up in IntelliSense**: Updates to Razor Components defined in .razor files may fail to show up in IntelliSense in Visual Studio. To workaround this issue rebuild the project.

- **Single Page Applications with authentication enabled throws method not found exception when visiting the register or login pages**: The exception message is the one below.
`Method not found: 'Microsoft.EntityFrameworkCore.Metadata.Builders.IndexBuilder Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder``1.HasIndex(System.Linq.Expressions.Expression``1<System.Func``2<!0,System.Object>>)'.` To workaround this issue follow these steps:
  * Replace the following package references with the ones below in your csproj folder:
    ```xml
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.0.0-preview3-19153-02" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="3.0.0-preview3.19153.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.0.0-preview3.19153.1" />
    ```

    ```xml
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.0.0-preview-18579-0056" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="3.0.0-preview.19080.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.0.0-preview.19080.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="3.0.0-preview.19080.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.0.0-preview.19080.1" />
    ```

  * Add the following snippet to your csproj file:
    ```xml
    <PropertyGroup>
      <NoWarn>$(NoWarn);NU1605</NoWarn>
    </PropertyGroup>
    ```
    
- **Referencing 3.0.0 MVC libraries don't work as intended**: There are several issues with referencing a 3.0.0 MVC library.

    * Razor pages will 404, 
    * ApplicationParts and factories will not be discoverable
    * Controllers will not be discoverable

    To workaround this issue do the following:

    * Add the helper method:
    ```C#
    private void Add30AssemblyWorkaround(Assembly referencedAssembly, ApplicationPartManager applicationPartManager)
    {
        var partFactory = ApplicationPartFactory.GetApplicationPartFactory(referencedAssembly);

        foreach (var part in partFactory.GetApplicationParts(referencedAssembly))
        {
            applicationPartManager.ApplicationParts.Add(part);
        }

        var relatedAssemblies = RelatedAssemblyAttribute.GetRelatedAssemblies(referencedAssembly, throwOnError: true);
        foreach (var assembly in relatedAssemblies)
        {
            partFactory = ApplicationPartFactory.GetApplicationPartFactory(assembly);
            foreach (var part in partFactory.GetApplicationParts(assembly))
            {
                applicationPartManager.ApplicationParts.Add(part);
            }
        }
    }
    ```

    * Modify your `services.AddMvc()` call in `Startup.cs`:
    ```
    services.AddMvc()
        .ConfigureApplicationPartManager(manager =>
        {
            var referencedAssembly = Assembly.Load("RCL");
            Add30AssemblyWorkaround(referencedAssembly, manager);
        })
        ...
    ```