SqlConnectionStringBuilder.ConnectionString returns empty string in net6.0 when using Microsoft.Data.SqlClient 6.1.x

[kuanpak]

Describe the bug

Microsoft.Data.SqlClient.SqlConnectionStringBuilder.ConnectionString always returns empty in .NET 6 target framework when using Microsoft.Data.SqlClient v6.1.x package.

To reproduce

Reproduce option 1:

Create a console csporj as below:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Data.SqlClient" Version="6.1.2" />
  </ItemGroup>

</Project>

Program.cs:

var connstrBuilder = new Microsoft.Data.SqlClient.SqlConnectionStringBuilder("Data Source=localhost;");
Console.WriteLine($"Connection String: {connstrBuilder.ConnectionString}");  // returns empty string in net6.0 when using Microsoft.Data.SqlClient 6.1.x

Run the above program will output below message in console:
Connection String:

Reproduce option 2:

Run below command in bash under Linux with docker installed:

docker run -it --rm mcr.microsoft.com/dotnet/sdk:6.0 bash -c "\
  dotnet new console -n demo && \
  dotnet add demo package Microsoft.Data.SqlClient -v 6.1.2 && \
  echo 'Console.WriteLine($\"Connection String: {new Microsoft.Data.SqlClient.SqlConnectionStringBuilder(\"Data Source=localhost;\").ConnectionString}\");' >> demo/Program.cs &&\
  dotnet run -p demo; bash"

Expected behavior

The program should output below message in console:
Connection String: Data Source=localhost

Further technical details

Microsoft.Data.SqlClient version: 6.1.2
.NET target: .NET 6.0
SQL Server version: N/A
Operating system: Windows 10/11, Ubuntu 24.04 WSL, Docker container

[ErikEJ]

SqlClient 6 does not support .NET 6, which is out of support.

Use 5.x or use .NET 8 or newer.

[mdaigle]

Closing due to unsupported version/framework combo. Please reopen if you reproduce the issue with a supported combo.

[hmassa]

Looks like the NuGet.org page for SqlClient 6.1.x lists .NET 6 as a compatible framework for some reason. I imagine that will cause some confusion here.

https://www.nuget.org/packages/Microsoft.Data.SqlClient/6.1.2#supportedframeworks-body-tab

[mdaigle]

@hmassa that page is a little confusing, the highlighted frameworks are the ones that are targeted by the package. You'll see that only net8.0, net9.0, net462, and netstandard2.0 are targeted.