dotnet-msbuild-tasks

name	dotnet-msbuild-tasks
category	developer-experience
subcategory	msbuild
description	Writes custom MSBuild tasks. ITask, ToolTask, IIncrementalTask, inline tasks, UsingTask.
license	MIT
targets	["*"]
tags	["foundation","dotnet","skill"]
version	0.0.1
author	dotnet-agent-harness
invocable	true
claudecode	{"allowed-tools":["Read","Grep","Glob","Bash","Write","Edit"]}
codexcli	{"short-description":".NET skill guidance for foundation tasks"}
opencode	{"allowed-tools":["Read","Grep","Glob","Bash","Write","Edit"]}
copilot	{}
geminicli	{}
antigravity	{}

dotnet-msbuild-tasks

Guidance for authoring custom MSBuild tasks: implementing the ITask interface, extending ToolTask for CLI wrappers, using IIncrementalTask (MSBuild 17.8+) for incremental execution, defining inline tasks with CodeTaskFactory, registering tasks via UsingTask, declaring task parameters, debugging tasks, and packaging tasks as NuGet packages.

Version assumptions: .NET 8.0+ SDK (MSBuild 17.8+). IIncrementalTask requires MSBuild 17.8+ (VS 2022 17.8+, .NET 8 SDK). All examples use SDK-style projects. All C# examples assume using Microsoft.Build.Framework; and using Microsoft.Build.Utilities; are in scope unless shown explicitly.

Scope

• ITask interface and Task base class implementation
• ToolTask for wrapping external CLI tools
• IIncrementalTask for engine-filtered incremental execution
• Inline tasks with CodeTaskFactory
• UsingTask registration and task parameters
• Task debugging and NuGet packaging

Out of scope

• MSBuild project system authoring (targets, props, items, conditions) -- see [skill:dotnet-msbuild-authoring]

Cross-references: [skill:dotnet-msbuild-authoring] for custom targets, import ordering, items, conditions, and property functions.

---

ITask Interface

All MSBuild tasks implement Microsoft.Build.Framework.ITask. The simplest approach is to inherit from Microsoft.Build.Utilities.Task, which provides default implementations for BuildEngine and HostObject.

Minimal Custom Task

using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

public class GenerateFileHash : Task
{
    [Required]
    public string InputFile { get; set; } = string.Empty;

    [Output]
    public string Hash { ; ; } = .Empty;

    
    {
         (!File.Exists(InputFile))
        {
            Log.LogError(, InputFile);
             ;
        }

          stream = File.OpenRead(InputFile);
         bytes = System.Security.Cryptography.SHA256.HashData(stream);
        Hash = Convert.ToHexString(bytes).ToLowerInvariant();

        Log.LogMessage(MessageImportance.Normal,
            , InputFile, Hash);
         ;
    }
}