IHostBuilder does not contain a definition for ConfigureWebHostDefaults

问题

I'm trying to use the new GenericHost in .NET Core 3.0 documented here but I'm getting a really basic error that stats IHostBuilder does not contain a definition for the ConfigureWebHostDefaults function.

Looking at the ASP.NET 3.0 documentation here for the IHostBuilder interface here I cant see any reference to ConfigureWebHostDefaults so I'm a bit confused.

I'm using the 3.0.0 packages for Microsoft.Extensions.Hosting and Microsoft.Extensions.Hosting.Abstractions but cant help but feel I'm either missing something really obvious or that ConfigureWebHostDefaults has for some reason been removed?

Update -- Screen shot of Program.cs

Update -- .csproj file

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Hosting" Version="2.2.7" />
    <PackageReference Include="Microsoft.Extensions.Hosting" Version="3.0.0" />
    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="3.0.0" />
  </ItemGroup>

</Project>

回答1:

Along with using Microsoft.Extensions.Hosting, ConfigureWebHostDefaults also require using Microsoft.AspNetCore.Hosting; as follows:

using Microsoft.AspNetCore.Hosting; //<-- Here it is
using Microsoft.Extensions.Hosting;

namespace MyApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateWebHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();
                });
    }
}

Moreover it look like your project is a Console Application. That is the problem. ConfigureWebHostDefaults is for Web Application only. So you can convert your Console Application into Web Applicaton by replacing Sdk="Microsoft.NET.Sdk" with Sdk="Microsoft.NET.Sdk.Web" in your .csproj file as follows:

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <AspNetCoreHostingModel>InProcess</AspNetCoreHostingModel>
  </PropertyGroup>

</Project>

来源：https://stackoverflow.com/questions/58097568/ihostbuilder-does-not-contain-a-definition-for-configurewebhostdefaults

标签

asp.net-core-3.0