Problem deploying C# Function App to Azure from Azure Devops pipeline

Question

Problem deploying C# Function App to Azure from Azure Devops pipeline

Paul D'hertoghe 20

I have a C# function app solution that I can deploy from Visual Studio to Azure. It works.

When I create an Azure Devops build pipeline and perform a build and deploy to Azure, the function app fails to start. The error I see using application insights|Failures is:

dotnet exited with code 134 (0x86) Unhandled exception. System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Bcl.AsyncInterfaces, Version=8.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.

When I check the zip artifact after the build, the zip contains version 8.0.0.0 of the MicroSoft.Bcl.AsyncInterfaces.assembly.
Maybe not unimportant: the Azure function is hosted on a linux runtime.

What could be wrong?

Paul D'hertoghe 20

I will post some additional files that could be relevant.
This is the publish profile from Visual Studio (apconnectairecognition-dev-staging - Zip Deploy.pubxml):

<?xml version="1.0" encoding="utf-8"?>

<!--

https://go.microsoft.com/fwlink/?LinkID=208121.

-->

<WebPublishMethod>ZipDeploy</WebPublishMethod>

<PublishProvider>AzureWebSite</PublishProvider>

<LastUsedBuildConfiguration>Release</LastUsedBuildConfiguration>

<LastUsedPlatform>Any CPU</LastUsedPlatform>

<SiteUrlToLaunchAfterPublish>https://apconnectairecognition-dev.azurewebsites.net</SiteUrlToLaunchAfterPublish>

<LaunchSiteAfterPublish>false</LaunchSiteAfterPublish>

<ResourceId>/subscriptions/...../resourceGroups/ai.recognition-dev-rg/providers/Microsoft.Web/sites/APconnectAIRecognition-dev</ResourceId>

<UserName>$APconnectAIRecognition-dev</UserName>

<_SavePWD>true</_SavePWD>

<IsLinux>true</IsLinux>

<RuntimeIdentifier>linux-x64</RuntimeIdentifier>

<PublishUrl>https://apconnectairecognition-dev.scm.azurewebsites.net/</PublishUrl>

</PropertyGroup>

</Project>

Paul D'hertoghe 20

This is the csproj file:
<Project Sdk="Microsoft.NET.Sdk">

<TargetFramework>net8.0</TargetFramework>

<RuntimeIdentifiers>win-x64;linux-x64</RuntimeIdentifiers>

<AzureFunctionsVersion>v4</AzureFunctionsVersion>

<OutputType>Exe</OutputType>

<ImplicitUsings>enable</ImplicitUsings>

<Nullable>enable</Nullable>

</PropertyGroup>

<FrameworkReference Include="Microsoft.AspNetCore.App" />

<PackageReference Include="Azure.AI.OpenAI" Version="2.1.0" />

<PackageReference Include="Microsoft.Azure.Functions.Worker" Version="2.0.0" />

<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.2.0" />

<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="2.0.0" />

<PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="2.0.0" />

<PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.22.0" />

<PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="2.0.0" />

<PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" />

<PackageReference Include="Newtonsoft.Json.Schema" Version="4.0.1" />

</ItemGroup>

<ProjectReference Include="..\AI.Recognition.OpenAI\AI.Recognition.OpenAI.csproj" />

</ItemGroup>

<None Update="host.json">

  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>

</None>

<None Update="local.settings.json">

  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>

  <CopyToPublishDirectory>Never</CopyToPublishDirectory>

</None>

</ItemGroup>

<Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />

</ItemGroup>

</Project>

Paul D'hertoghe 20 Reputation points

2025-06-12T08:08:14.7633333+00:00
This is the yaml file:

.NET Core Function App to Windows on Azure

Build a .NET Core function app and deploy it to Azure as a Windows function App.

Add steps that analyze code, save build artifacts, deploy, and more:

https://docs.microsoft.com/en-us/azure/devops/pipelines/languages/dotnet-core

trigger: none # will disable CI builds (but not PR builds)

pr: none # will disable PR builds (but not CI builds)

variables:

dev

dev-subscription: 'RecoMatics Customer DEV'

dev-resourceGroupName: 'ai.recognition-dev-rg'

dev-functionAppName: 'APconnectAIRecognition-DEV'

dev-keyVaultName: 'APcAIRecognition-DEV'

production

azureSubscription: 'Recomatics EasyForm.Cloud Shared Production(2a8663a8-ac75-4b45-96ef-370ee4daf3ca)'

resourceGroupName: 'easyformcloud-ai.recognition-prod-rg'

functionAppName: 'APconnectAIRecognition-production'

keyVaultName: 'APconnectAIRecognition'

Working Directory

workingDirectory: '$(System.DefaultWorkingDirectory)/Sources/Service'

bicepFile: '$(System.DefaultWorkingDirectory)/main.bicep'

artifactPath: '$(Pipeline.Workspace)/drop/$(Build.BuildId).zip'

stages:

stage: Build displayName: Build stage jobs:

job: Build displayName: Build pool: name: 'Private Azure MSDN' steps:

task: NuGetToolInstaller@1 inputs: versionSpec:

task: NuGetCommand@2 displayName: 'Authenticate with our private NuGet feed' inputs: command: custom arguments: sources update -Name "RecoMatics" -Username "vsts" -Password "$(System.AccessToken)" -StorePasswordInClearText -ConfigFile ./NuGet.Config

task: UseDotNet@2 displayName: 'Use dotnet sdk 8.0.x' inputs: packageType: 'sdk' version: '8.0.x'

task: DotNetCoreCLI@2 displayName: Restore inputs: command: 'restore' projects: 'Sources/Service/**/*.csproj' arguments: '--configuration Release --runtime linux-x64'

task: DotNetCoreCLI@2 displayName: Publish inputs: command: 'publish' publishWebProjects: false projects: '$(workingDirectory)/**/*.csproj' arguments: '--configuration Release --output $(System.DefaultWorkingDirectory)/publish_output --no-restore --runtime linux-x64'

task: ArchiveFiles@2 displayName: 'Archive files' inputs: rootFolderOrFile: '$(System.DefaultWorkingDirectory)/publish_output' includeRootFolder: false archiveType: zip archiveFile: $(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip replaceExistingArchive: true

publish: $(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip artifact: drop

stage: DeployToDev displayName: Deploy to dev dependsOn: Build condition: succeeded() jobs:

template: FunctionApp-Deploy_Template.yml parameters: azureSubscription: '$(dev-subscription)' environmentName: 'dev' resourceGroupName: '$(dev-resourceGroupName)' functionAppName: '$(dev-functionAppName)' keyVaultName: '$(dev-keyVaultName)' artifactPath: '$(artifactPath)' bicepFile: $(bicepFile) azureOpenAIChatGpt4oMiniBaseUrl: $(dev-azureOpenAIChatGpt4oMiniBaseUrl) azureOpenAIChatGpt4oMiniApiKey: $(dev-azureOpenAIChatGpt4oMiniApiKey) azureOpenAIChatGpt4oBaseUrl: $(dev-azureOpenAIChatGpt4oBaseUrl) azureOpenAIChatGpt4oApiKey: $(dev-azureOpenAIChatGpt4oApiKey) azureOpenAIChatGpt41MiniBaseUrl: $(dev-azureOpenAIChatGpt41MiniBaseUrl) azureOpenAIChatGpt41MiniApiKey: $(dev-azureOpenAIChatGpt41MiniApiKey)

stage: DeployToProduction displayName: Deploy to Production trigger: manual jobs:

template: FunctionApp-Deploy_Template.yml parameters: azureSubscription: '$(azureSubscription)' environmentName: 'production' resourceGroupName: '$(resourceGroupName)' functionAppName: '$(functionAppName)' keyVaultName: '$(keyVaultName)' artifactPath: '$(artifactPath)' bicepFile: $(bicepFile) azureOpenAIChatGpt4oMiniBaseUrl: $(azureOpenAIChatGpt4oMiniBaseUrl) azureOpenAIChatGpt4oMiniApiKey: $(azureOpenAIChatGpt4oMiniApiKey) azureOpenAIChatGpt4oBaseUrl: $(azureOpenAIChatGpt4oBaseUrl) azureOpenAIChatGpt4oApiKey: $(azureOpenAIChatGpt4oApiKey) azureOpenAIChatGpt41MiniBaseUrl: $(azureOpenAIChatGpt4oMiniBaseUrl) azureOpenAIChatGpt41MiniApiKey: $(azureOpenAIChatGpt4oMiniApiKey)

Paul D'hertoghe 20

This is a utility yaml file:

deploy-template.yml

parameters:

name: azureSubscription type: string
name: environmentName type: string
name: resourceGroupName type: string
name: functionAppName type: string
name: keyVaultName type: string
name: artifactPath type: string
name: location type: string default: 'westeurope'
name: bicepFile type: string
name: azureOpenAIChatGpt4oMiniApiKey type: string default: 'dummy'
name: azureOpenAIChatGpt4oMiniBaseUrl type: string default: 'dummy'
name: azureOpenAIChatGpt4oApiKey type: string default: 'dummy'
name: azureOpenAIChatGpt4oBaseUrl type: string default: 'dummy'
name: azureOpenAIChatGpt41MiniApiKey type: string default: 'dummy'
name: azureOpenAIChatGpt41MiniBaseUrl type: string default: 'dummy'

jobs:

job: ResourceMgmt displayName: 'Resource Management for ${{ parameters.environmentName }}' steps:

task: AzureCLI@2 inputs: azureSubscription: '${{ parameters.azureSubscription }}' scriptType: 'pscore' scriptLocation: 'inlineScript' inlineScript: |

az group create --name ${{ parameters.resourceGroupName }} --location ${{ parameters.location }}

az keyvault create --name ${{ parameters.keyVaultName }} --resource-group ${{ parameters.resourceGroupName }} --location ${{ parameters.location }} --enabled-for-template-deployment true

az keyvault secret set --vault-name ${{ parameters.keyVaultName }} --name "azureOpenAIChatGpt4oMiniApiKey" --value ${{ parameters.azureOpenAIChatGpt4oMiniApiKey }}

az keyvault secret set --vault-name ${{ parameters.keyVaultName }} --name "azureOpenAIChatGpt4oApiKey" --value ${{ parameters.azureOpenAIChatGpt4oApiKey }}

az keyvault secret set --vault-name ${{ parameters.keyVaultName }} --name "azureOpenAIChatGpt41MiniApiKey" --value ${{ parameters.azureOpenAIChatGpt41MiniApiKey }}

az deployment group create --resource-group ${{ parameters.resourceGroupName }} --template-file ${{ parameters.bicepFile }} --parameters environmentName=${{ parameters.environmentName }} kvName=${{ parameters.keyVaultName }} azureOpenAIChatGpt4oBaseUrl=${{ parameters.azureOpenAIChatGpt4oBaseUrl }}  azureOpenAIChatGpt4oMiniBaseUrl=${{ parameters.azureOpenAIChatGpt4oMiniBaseUrl }} azureOpenAIChatGpt41MiniBaseUrl=${{ parameters.azureOpenAIChatGpt41MiniBaseUrl }}

deployment: DeployToStaging dependsOn: ResourceMgmt displayName: 'Deploy to staging slot of ${{ parameters.environmentName }}' environment: '${{ parameters.environmentName }}' strategy: runOnce:

deploy:

  steps:

  - task: AzureFunctionApp@2

    displayName: 'Azure Function App Deployment'

    inputs:

      connectedServiceNameARM: '${{ parameters.azureSubscription }}'

      appType: 'functionAppLinux'

      runtimeStack: 'DOTNET-ISOLATED|8.0'

      appName: '${{ parameters.functionAppName }}'

      slotName: 'staging'

      package: '${{ parameters.artifactPath }}'

Accepted answer

1 additional answer

Your answer

Paul D'hertoghe 20 Reputation points

2025-06-12T08:06:36.54+00:00

I will post some additional files that could be relevant.
This is the publish profile from Visual Studio (apconnectairecognition-dev-staging - Zip Deploy.pubxml):

<?xml version="1.0" encoding="utf-8"?>



<Project>

<PropertyGroup>

<WebPublishMethod>ZipDeploy</WebPublishMethod> <PublishProvider>AzureWebSite</PublishProvider> <LastUsedBuildConfiguration>Release</LastUsedBuildConfiguration> <LastUsedPlatform>Any CPU</LastUsedPlatform> <SiteUrlToLaunchAfterPublish>https://apconnectairecognition-dev.azurewebsites.net</SiteUrlToLaunchAfterPublish> <LaunchSiteAfterPublish>false</LaunchSiteAfterPublish> <ResourceId>/subscriptions/...../resourceGroups/ai.recognition-dev-rg/providers/Microsoft.Web/sites/APconnectAIRecognition-dev</ResourceId> <UserName>$APconnectAIRecognition-dev</UserName> <_SavePWD>true</_SavePWD> <IsLinux>true</IsLinux> <RuntimeIdentifier>linux-x64</RuntimeIdentifier> <PublishUrl>https://apconnectairecognition-dev.scm.azurewebsites.net/</PublishUrl>

</PropertyGroup>

</Project>
Paul D'hertoghe 20 Reputation points

2025-06-12T08:07:11.3633333+00:00

This is the csproj file:
<Project Sdk="Microsoft.NET.Sdk">

<PropertyGroup>

<TargetFramework>net8.0</TargetFramework> <RuntimeIdentifiers>win-x64;linux-x64</RuntimeIdentifiers> <AzureFunctionsVersion>v4</AzureFunctionsVersion> <OutputType>Exe</OutputType> <ImplicitUsings>enable</ImplicitUsings> <Nullable>enable</Nullable>

</PropertyGroup>

<ItemGroup>

<FrameworkReference Include="Microsoft.AspNetCore.App" /> <PackageReference Include="Azure.AI.OpenAI" Version="2.1.0" /> <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="2.0.0" /> <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.2.0" /> <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http.AspNetCore" Version="2.0.0" /> <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="2.0.0" /> <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.22.0" /> <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="2.0.0" /> <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" /> <PackageReference Include="Newtonsoft.Json.Schema" Version="4.0.1" />

</ItemGroup>

<ItemGroup>

<ProjectReference Include="..\AI.Recognition.OpenAI\AI.Recognition.OpenAI.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>

<Using Include="System.Threading.ExecutionContext" Alias="ExecutionContext" />

</ItemGroup>

</Project>

Answer 1

Hi @Paul D'hertoghe,

I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this.

Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.

Issue :

Azure Function App fails to start after being deployed from Azure DevOps

Solution :

the publish devops task needs self-contained to be set to true. It seems that the default linux environment doesn't have .NET 8 installed?

The default Linux environment for Azure Functions currently does not support .NET 8 as a framework-dependent runtime.
If you don't set --self-contained true, your app assumes that .NET 8 is already installed on the Azure Function host.
The latest working DevOps task you provided creates a self-contained deployment that bundles the .NET runtime and all necessary dependencies, ensuring it runs smoothly in Azure Linux Function environments.

Please click Accept Answer and kindly upvote it so that other people who faces similar issue may get benefited from it.

Answer 2

Paul D'hertoghe 20

I found the solution: the publish devops task needs self-contained to be set to true. It seems that the default linux environment doesn't have .NET 8 installed?

- task: DotNetCoreCLI@2

  displayName: Publish

  inputs:

    command: 'publish'

    publishWebProjects: false

    projects: '$(workingDirectory)/**/*.csproj'

    arguments: '--configuration Release --output $(System.DefaultWorkingDirectory)/publish_output --no-restore --runtime linux-x64 --self-contained true'

Paul D'hertoghe 20 Reputation points

2025-06-12T08:45:37.1633333+00:00

Can someone of the Azure function app deployment team look at this, because this is a hard to find issue. Additional logging or error checking during upload would be welcome!

Share via

Problem deploying C# Function App to Azure from Azure Devops pipeline

.NET Core Function App to Windows on Azure

Build a .NET Core function app and deploy it to Azure as a Windows function App.

Add steps that analyze code, save build artifacts, deploy, and more:

https://docs.microsoft.com/en-us/azure/devops/pipelines/languages/dotnet-core

dev

production

Working Directory

deploy-template.yml

1 additional answer

Your answer