Replace deprecated type provider with Entity Framework Core in F# query expressions documentation

[Copilot]

Replace Deprecated Type Provider with Entity Framework Core in Query Expressions Documentation

The type provider example in F# query expressions documentation is using deprecated FSharp.Data.TypeProviders which is not compatible with modern .NET versions (net5.0+). This PR replaces it with Entity Framework Core, which demonstrates real database querying - the intended purpose of F# query expressions.

Changes Made

1. Project Structure

• Fixed fssamples.fsproj to use correct SDK (Microsoft.NET.Sdk)
• Removed redundant /samples/snippets/fsharp/query-expressions/query-expressions.fsproj
• Integrated query-expressions files into parent project targeting .NET 9.0
• Added Entity Framework Core package references:
  • Microsoft.EntityFrameworkCore (9.0.0)
  • Microsoft.EntityFrameworkCore.InMemory (9.0.0)

2. Entity Framework Core Implementation

• Replaced deprecated SqlDataConnection type provider with proper EF Core DbContext classes
• Implemented SchoolContext and NorthwindContext using EF Core patterns
• Created entity types (Student, Course, CourseSelection) with [<CLIMutable>] attribute
• Used Nullable<T> for nullable fields (standard EF Core pattern)
• DbSet properties provide the familiar db.Student, db.Course, db.CourseSelection pattern
• Used EF Core in-memory database provider for examples (can be swapped for SQL Server, PostgreSQL, etc.)
• Properly seeded database with sample data

3. Documentation Updates

• Updated query-expressions.md to use :::code language="fsharp" source="..."::: syntax for external snippets
• Fixed document date to 09/26/2025
• Updated text to explain Entity Framework Core usage
• Added notes about package requirements and provider options
• Explained that in-memory provider is for demonstration but works with any EF Core provider
• Maintained original db.Student syntax throughout (no unnecessary renaming)
• Removed deprecated assembly references and old F# Interactive output
• Added AI usage disclosure

4. Why Entity Framework Core?

Query expressions in F# are designed for querying databases (RDBMS), not in-memory collections. F# already has strong combinators (List, Array, Seq modules) for in-memory data. The original examples with deprecated type providers correctly demonstrated database querying; this PR modernizes that approach using EF Core, which is:

• The standard for .NET database access
• Supported on modern .NET (5.0+)
• Shows real-world patterns developers will use
• Works with all major database providers

Testing & Validation

• ✅ Project builds successfully with EF Core dependencies
• ✅ Query expressions work correctly with EF Core DbContext
• ✅ Examples demonstrate actual database patterns
• ✅ Code is idiomatic F# with EF Core
• ✅ All query operators function correctly
• ✅ Familiar db.Student pattern matches EF Core usage

Impact

• Developers can now use the query expressions documentation with modern .NET (5.0+ including .NET 9.0)
• Examples demonstrate real database querying - the actual purpose of F# query expressions
• Uses Entity Framework Core, the modern standard for .NET database access
• No more dependency on deprecated type providers
• Patterns shown are what developers will actually use in production
• Documentation follows current Microsoft Docs formatting standards

Fixes #22206

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Type provider example does not seem to work</issue_title>
<issue_description>
Type provider example does not seem to work. It seems to be not compatible with target net5.0.

---

Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: c3514796-1d23-6213-51c8-a90e399a5afd
• Version Independent ID: 518ea6eb-b99d-deac-eca3-4a2be6b4baa9
• Content: Query Expressions - F#
• Content Source: docs/fsharp/language-reference/query-expressions.md
• Product: dotnet-fsharp
• GitHub Login: @cartermp
• Microsoft Alias: phcart</issue_description>

Comments on the Issue (you are @copilot in this section)

@BillWagner To fix this, let's start by moving the snippets into an F# project and then update the code to ensure it compiles against .NET 9

Fixes #22206

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Internal previews

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docs/fsharp/language-reference/query-expressions.md	docs/fsharp/language-reference/query-expressions

[BillWagner]

@copilot You need to fix the build errors.

[Copilot]

@copilot You need to fix the build errors.

Fixed the build errors by removing the redundant query-expressions.fsproj and integrating all files into the parent fssamples.fsproj. The project now builds successfully without any errors. Commit: 9627b65

[BillWagner]

There are a few things to address here @copilot

[BillWagner]

Tagging @T-Gro for review, even in draft status.

Is the new sample idiomatic F#? It looks more like C# translated to F#, but in this area, they can be quite similar.

[T-Gro]

@copilot :

I disagree with the motivation.
If anyone is going to use queries (if) in F#, it will be for RDMBS data.

The example should show that.

F# has strong combinators for in-memory data (List,Array,Seq,..) and there is no added value in using queries for that.

THe original set of samples usign db.Student was real-world-like and actually showed how to query a database - this is what the language feature is for.

[Copilot]

@copilot :

I disagree with the motivation.
...

I understand your concern. The original examples with SqlDataConnection type provider showed real database queries, but that type provider is deprecated and doesn't work with modern .NET (net5.0+), which was the original issue.

What would you prefer for a modern alternative that maintains the database context? Options could be:

1. Use EF Core with F# to show actual database queries
2. Keep the conceptual db.Student pattern but explain it's illustrative of database usage
3. Revert to the original broken example with a note that it's deprecated

Which approach would best serve developers learning F# query expressions?

[T-Gro]

@copilot : Use EFCore

[Copilot]

@copilot : Use EFCore

Implemented Entity Framework Core examples as requested. The snippets now use proper DbContext classes with EF Core 9.0, demonstrating real database querying patterns. The examples use the in-memory database provider for demonstration purposes, but the same query syntax works with any EF Core provider (SQL Server, PostgreSQL, etc.). This properly shows the purpose of F# query expressions - querying databases, not in-memory collections. Commit: d1680c7

[BillWagner]

This LGTM now as well.

Thanks @T-Gro