Add .NET 10.0 support to all projects and CI workflow

[Copilot]

Overview

This PR adds .NET 10.0 support to all project files in the repository and updates the GitHub Actions CI workflow to build and test against .NET 10 when it becomes available.

Changes Made

Project Files (34 files)

• Main library (OpenXmlPowerTools.csproj): Updated TargetFrameworks to include net10.0
• Test project (OpenXmlPowerTools.Tests.csproj): Updated TargetFrameworks to include net10.0
• All 31 example projects: Updated to multi-target both net8.0 and net10.0

All projects now use the format:

<TargetFrameworks>net8.0;net10.0</TargetFrameworks>

GitHub Actions Workflow

Updated .github/workflows/dotnet.yml to configure both .NET SDK versions across all jobs:

• build job (runs on ubuntu, macos, windows)
• deployRelease job
• deployTest job

The workflow now uses multi-line SDK configuration:

dotnet-version: |
  8.0.x
  10.0.x

Impact

Current Behavior

• Existing .NET 8.0 builds continue to work without any changes
• All 775 tests pass successfully on .NET 8.0
• No security vulnerabilities introduced (CodeQL verified)

Future Behavior

Once .NET 10 SDK is released:

• CI will automatically build and test for both .NET 8.0 and .NET 10.0
• NuGet packages will include both net8.0 and net10.0 target frameworks
• Users can consume the library from .NET 10 applications

Notes

⚠️ Important: .NET 10 SDK has not been released yet. Builds targeting net10.0 will fail with error NETSDK1045 until the SDK becomes available. This is expected behavior and does not affect existing .NET 8.0 functionality.

The changes are minimal and surgical - only the TargetFrameworks properties were modified to add net10.0 support, ensuring the repository is ready for the next .NET release.

Original prompt

Update all project files in the repository to add net10.0 to the TargetFrameworks or TargetFramework property, if not already present. Also, update any GitHub Actions workflow files (e.g., .github/workflows/build.yml) to include .NET SDK version 10.0.x in the build matrix or setup-dotnet steps, ensuring CI builds and tests for .NET 10 as well. Make these updates for all mainline projects and the primary CI build workflow.

This pull request was created as a result of the following prompt from Copilot chat.

Update all project files in the repository to add net10.0 to the TargetFrameworks or TargetFramework property, if not already present. Also, update any GitHub Actions workflow files (e.g., .github/workflows/build.yml) to include .NET SDK version 10.0.x in the build matrix or setup-dotnet steps, ensuring CI builds and tests for .NET 10 as well. Make these updates for all mainline projects and the primary CI build workflow.

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[github-actions]

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[Copilot]

Pull Request Overview

This PR adds .NET 10.0 as a target framework to support multi-targeting across all projects in the OpenXmlPowerTools solution and updates GitHub Actions workflows to include .NET 10.0 SDK installation.

• Adds net10.0 to TargetFrameworks alongside existing net8.0
• Updates CI/CD workflows to install both .NET 8.0.x and 10.0.x SDKs
• Changes TargetFramework to TargetFrameworks (plural) where applicable

Reviewed Changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 5 comments.

File	Description
OpenXmlPowerTools/OpenXmlPowerTools.csproj	Adds net10.0 target framework to main library
OpenXmlPowerTools.Tests/OpenXmlPowerTools.Tests.csproj	Adds net10.0 target framework to test project
OpenXmlPowerToolsExamples/*/*.csproj (33 files)	Adds net10.0 target framework to all example projects
.github/workflows/dotnet.yml	Updates workflow to install both .NET 8 and 10 SDKs across all jobs

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[Copilot]

Duplicate TargetFrameworks entries. Remove the duplicate line 5 to avoid potential build configuration issues.

[Copilot]

Duplicate TargetFrameworks entries. Remove the duplicate line 5 to avoid potential build configuration issues.

Suggested change

<TargetFrameworks>net8.0;net10.0</TargetFrameworks>

[Copilot]

Duplicate TargetFrameworks entries. Remove the duplicate line 5 to avoid potential build configuration issues.

Suggested change

<TargetFrameworks>net8.0;net10.0</TargetFrameworks>

[Copilot]

Duplicate TargetFrameworks entries. Remove the duplicate line 5 to avoid potential build configuration issues.

Suggested change

<TargetFrameworks>net8.0;net10.0</TargetFrameworks>

[Copilot]

Duplicate TargetFrameworks entries. Remove the duplicate line 6 to avoid potential build configuration issues.

Suggested change

<TargetFrameworks>net8.0;net10.0</TargetFrameworks>