Getting asset file doesn't have targetframework exception while publishing in .net core project

Question

I don't understand how csproj and references play together. And I created a basic .Net Core app and it's building fine locally. But when I am trying to publish it I am getting exception as below.

error NETSDK1047: Assets file 'C:\Users\source\repos\AWSLambda7\AWSLambda7\obj\project.assets.json' doesn't have a target for '.NETCoreApp,Version=v3.1/linux-x64'. Ensure that restore has run and that you have included 'netcoreapp3.1' in the TargetFrameworks for your project. You may also need to include 'linux-x64' in your project's RuntimeIdentifiers. [C:\Users\source\repos\AWSLambda7\AWSLambda7\AWSLambda7.csproj]

Below is the code snippet

public class Function
{
    public async Task FunctionHandler(SQSEvent evnt, ILambdaContext context)
    {
        foreach (var message in evnt.Records)
        {
            await Task.CompletedTask;
        }
    }
}

The csproj file looks like below

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <GenerateRuntimeConfigurationFiles>true</GenerateRuntimeConfigurationFiles>
    <AWSProjectType>Lambda</AWSProjectType>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Amazon.Lambda.Core" Version="1.1.0" />
    <PackageReference Include="Amazon.Lambda.Serialization.SystemTextJson" Version="2.0.0" />
    <PackageReference Include="Amazon.Lambda.SQSEvents" Version="1.1.0" />
  </ItemGroup>
</Project>

The obj\project.assets.json file looks like below

{
  "version": 3,
  "targets": {
    ".NETCoreApp,Version=v3.1": {
      "Amazon.Lambda.Core/1.1.0": {
        "type": "package",
        "compile": {
          "lib/netstandard2.0/Amazon.Lambda.Core.dll": {}
        },
        "runtime": {
          "lib/netstandard2.0/Amazon.Lambda.Core.dll": {}
        }
      },
      "Amazon.Lambda.Serialization.SystemTextJson/2.0.0": {
        "type": "package",
        "dependencies": {
          "Amazon.Lambda.Core": "1.1.0"
        },
        "compile": {
          "lib/netcoreapp3.1/Amazon.Lambda.Serialization.SystemTextJson.dll": {}
        },
        "runtime": {
          "lib/netcoreapp3.1/Amazon.Lambda.Serialization.SystemTextJson.dll": {}
        }
      },
      "Amazon.Lambda.SQSEvents/1.1.0": {
        "type": "package",
        "compile": {
          "lib/netstandard2.0/Amazon.Lambda.SQSEvents.dll": {}
        },
        "runtime": {
          "lib/netstandard2.0/Amazon.Lambda.SQSEvents.dll": {}
        }
      }
    }
  },
  "libraries": {
    "Amazon.Lambda.Core/1.1.0": {
      "sha512": "ueGId8b4DEHoVWkHDs3iAJH8IUSAUGu5AqkoI/Syl4RuByzik7lz9IjoImQ==",
      "type": "package",
      "path": "amazon.lambda.core/1.1.0",
      "files": [
        ".nupkg.metadata",
        ".signature.p7s",
        "amazon.lambda.core.1.1.0.nupkg.sha512",
        "amazon.lambda.core.nuspec",
        "lib/netstandard1.3/Amazon.Lambda.Core.dll",
        "lib/netstandard1.3/Amazon.Lambda.Core.xml",
        "lib/netstandard2.0/Amazon.Lambda.Core.dll",
        "lib/netstandard2.0/Amazon.Lambda.Core.xml"
      ]
    },
    "Amazon.Lambda.Serialization.SystemTextJson/2.0.0": {
      "sha512": "En67XZpjBILNrLdb/7HqGtqkPjoRYDjViY4+PEn1CAe53FNStU/vbcVtDvDyvQeUnFgMui3zvMdlsjJIzBPHdQ==",
      "type": "package",
      "path": "amazon.lambda.serialization.systemtextjson/2.0.0",
      "files": [
        ".nupkg.metadata",
        ".signature.p7s",
        "amazon.lambda.serialization.systemtextjson.2.0.0.nupkg.sha512",
        "amazon.lambda.serialization.systemtextjson.nuspec",
        "lib/netcoreapp3.1/Amazon.Lambda.Serialization.SystemTextJson.dll",
        "lib/netcoreapp3.1/Amazon.Lambda.Serialization.SystemTextJson.xml"
      ]
    },
    "Amazon.Lambda.SQSEvents/1.1.0": {
      "sha512": "AD6rELASxItdSSR1Vj7X7pEE8OeGIADJkYer9dvHtXP+2Nhp==",
      "type": "package",
      "path": "amazon.lambda.sqsevents/1.1.0",
      "files": [
        ".nupkg.metadata",
        ".signature.p7s",
        "amazon.lambda.sqsevents.1.1.0.nupkg.sha512",
        "amazon.lambda.sqsevents.nuspec",
        "lib/netstandard1.3/Amazon.Lambda.SQSEvents.dll",
        "lib/netstandard1.3/Amazon.Lambda.SQSEvents.xml",
        "lib/netstandard2.0/Amazon.Lambda.SQSEvents.dll",
        "lib/netstandard2.0/Amazon.Lambda.SQSEvents.xml"
      ]
    }
  },
  "projectFileDependencyGroups": {
    ".NETCoreApp,Version=v3.1": [
      "Amazon.Lambda.Core >= 1.1.0",
      "Amazon.Lambda.SQSEvents >= 1.1.0",
      "Amazon.Lambda.Serialization.SystemTextJson >= 2.0.0"
    ]
  },
  "packageFolders": {
    "C:\\Users\\.nuget\\packages\\": {},
    "C:\\Program Files\\dotnet\\sdk\\NuGetFallbackFolder": {}
  },
  "project": {
    "version": "1.0.0",
    "restore": {
      "projectUniqueName": "C:\\Users\\source\\repos\\AWSLambda7\\AWSLambda7\\AWSLambda7.csproj",
      "projectName": "AWSLambda7",
      "projectPath": "C:\\Users\\source\\repos\\AWSLambda7\\AWSLambda7\\AWSLambda7.csproj",
      "packagesPath": "C:\\Users\\.nuget\\packages\\",
      "outputPath": "C:\\Users\\source\\repos\\AWSLambda7\\AWSLambda7\\obj\\",
      "projectStyle": "PackageReference",
      "fallbackFolders": [
        "C:\\Program Files\\dotnet\\sdk\\NuGetFallbackFolder"
      ],
      "configFilePaths": [
        "C:\\Users\\AppData\\Roaming\\NuGet\\NuGet.Config",
        "C:\\Program Files (x86)\\NuGet\\Config\\Microsoft.VisualStudio.Offline.config"
      ],
      "originalTargetFrameworks": [
        "netcoreapp3.1"
      ],
      "sources": {
        "C:\\Program Files (x86)\\Microsoft SDKs\\NuGetPackages\\": {},
        "https://api.nuget.org/v3/index.json": {}
      },
      "frameworks": {
        "netcoreapp3.1": {
          "projectReferences": {}
        }
      },
      "warningProperties": {
        "warnAsError": [
          "NU1605"
        ]
      }
    },
    "frameworks": {
      "netcoreapp3.1": {
        "dependencies": {
          "Amazon.Lambda.Core": {
            "target": "Package",
            "version": "[1.1.0, )"
          },
          "Amazon.Lambda.SQSEvents": {
            "target": "Package",
            "version": "[1.1.0, )"
          },
          "Amazon.Lambda.Serialization.SystemTextJson": {
            "target": "Package",
            "version": "[2.0.0, )"
          }
        },
        "imports": [
          "net461",
          "net462",
          "net47",
          "net471",
          "net472",
          "net48"
        ],
        "assetTargetFallback": true,
        "warn": true,
        "frameworkReferences": {
          "Microsoft.NETCore.App": {
            "privateAssets": "all"
          }
        },
        "runtimeIdentifierGraphPath": "C:\\Program Files\\dotnet\\sdk\\3.1.301\\RuntimeIdentifierGraph.json"
      }
    }
  }
}

Note that project builds fine in VS-2019 in Windows 10 machine.

Bharath Kumar Reddy Bharath Kumar Reddy · Accepted Answer · 2020-12-10T18:07:37

I think you are building a project directly. which will by default will support windows server, AWS lambda internally will use Linux OS. We need to Build & Package target OS as Linux Below are some of the steps you need to follow

Make sure you are added a Lambda serializer Below is code for the same [assembly:LambdaSerializer(typeof(DefaultLambdaJsonSerializer))]
Open a Command prompt and execute this below command it will build and will package with the support of Aws lambda ready package (you must install AWS cli tools)

dotnet lambda package

If you don't have a AWS CLI tool use this below command

dotnet publish --output "[output folderpath]" --configuration "Release" --framework "netcoreapp3.1" /p:GenerateRuntimeConfigurationFiles=true --runtime linux-x64 --self-contained false

Getting asset file doesn't have targetframework exception while publishing in .net core project

1 Answers