Azure 函数 System.Net.Primitives：值不能是 null。 （参数“主机”）

Question

When I send an HTTP request to the function, It shows this error on console output, and returns HTTP 500 status code without hitting the the break point of function's first line.

Executed 'Validate' (Failed, Id=548b4612-42f8-4e49-886a-da6888045c32, Duration=343ms) System.Net.Primitives: Value cannot be null. (Parameter 'host') An unhandled host error has occurred. System.Net.Primitives: Value cannot be null. (Parameter 'host').

Function

[FunctionName("Validate")]
public async Task Run(
[HttpTrigger(AuthorizationLevel.Function, "post", Route = null)] string req,
[SignalR(HubName = "PubSub")] IAsyncCollector<SignalRMessage> signalRMessageQueue)
{
    ...
}

---

host.json

{
"version": "2.0",
"logging": {
  "applicationInsights": {
    "samplingExcludedTypes": "Request",
    "samplingSettings": {
      "isEnabled": true
    }
  }
}

---

.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
    <RootNamespace>ZulaMobile.Lobby.StoreValidation</RootNamespace>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
    <PackageReference Include="Microsoft.Azure.WebJobs" Version="3.0.30" />
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.SignalRService" Version="1.6.0" />
    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="3.1.21" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
  </ItemGroup>
  <ItemGroup>
    <ProjectReference Include="..\zulamobile-azure-lobby-common\zulamobile-azure-lobby-common.csproj" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
  <ItemGroup>
    <Folder Include="Functions\CafeBazaar\" />
    <Folder Include="Huawei\" />
  </ItemGroup>
</Project>

Answer 1

I tried to reproduce the same issue but it worked fine at my end. Followed by this MS DOC & demo GitHub project,

• Created a Signal IR in Azure portal.

Open the download folder from my VS Code-

And added the following packages into my local here is my .csproj file

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.WebJobs.Extensions.SignalRService" Version="1.6.0" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
  </ItemGroup>
  <ItemGroup>
    <None Update="content\index.html">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </None>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

And make sure that you have added your connection string in your local settings.json which have to copy from portal from Azure signalIR > Keys>Connection string.

Here are some screenshot for reference output:

Note: If still facing the same issue you can try to Un install the Azure function V3 and install it again.

For more information please refer this SO THREAD .