Code generated by NSwag.ApiDescription.Client 14.4.0 generates incorrect URLs

[rainerbossert]

Describe the bug

Code generated with NSwag.ApiDescription.Client 14.4.0 generates urls with enumerable int parameters a way that the standard WebApi model binder cannot handle.

using System.Globalization;

var builder144 = new System.Text.StringBuilder();

int[]? fundingSchemeIds = { 1, 2, 3 };

if (fundingSchemeIds != null)
{
    builder144.Append(System.Uri.EscapeDataString("FundingSchemeIds") + "=");
    foreach (var item_ in fundingSchemeIds)
    {
        builder144.Append(System.Uri.EscapeDataString(ConvertToString(item_, System.Globalization.CultureInfo.InvariantCulture))).Append(",");
    }
    builder144.Length--;
    builder144.Append("&");
}

Console.WriteLine("{0} // 14.4.0", builder144);

var builder143 = new System.Text.StringBuilder();

if (fundingSchemeIds != null)
{
    foreach (var item_ in fundingSchemeIds) { builder143.Append(System.Uri.EscapeDataString("FundingSchemeIds")).Append('=').Append(System.Uri.EscapeDataString(ConvertToString(item_, System.Globalization.CultureInfo.InvariantCulture))).Append('&'); }
}


Console.WriteLine("{0} // 14.3.0", builder143);
Console.Read();

string ConvertToString(int i, CultureInfo cultureInfo)
{
    return $"{i}";
}

Output

FundingSchemeIds=1,2,3& // 14.4.0 --> nok
FundingSchemeIds=1&FundingSchemeIds=2&FundingSchemeIds=3& // 14.3.0 --> ok

While the endpoint looks like

    [HttpGet(Name = nameof(SearchGrantsAsync))]
    [AllowAnonymous]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(SearchResult), StatusCodes.Status200OK)]
    public async Task<ActionResult<SearchResult>> SearchGrantsAsync([FromQuery] IEnumerable<int> fundingSchemeIds, CancellationToken cancellationToken)

Somehow similar to: #5096 (but the version 14.2.0 seems off).

Version of NSwag toolchain, computer and .NET runtime used

Nuget package NSwag.ApiDescription.Client --version 14.4.0

To Reproduce

Visual Studio 2022 (Version 17.13.6) right click on project using the service > Add > Connected Service > Service References > (Existing) Refresh

Expected behavior

The url generated in the client still works as it did before in Version 14.3.0

[alexfirs]

caused by #5016 - is not backward compatible unfortunately

[bifa-zuehlke]

The query format FundingSchemeIds=1,2,3 does not correctly bind to IEnumerable fundingSchemeIds in ASP.NET Core (.NET 6+). The default model binder expects repeated parameters like FundingSchemeIds=1&FundingSchemeIds=2&FundingSchemeIds=3 for correct binding.

How should we handle this @alexfirs?

[alexfirs]

@bifa-zuehlke i temporary downgraded to 14.2 until it fixed

[ThomasTosik]

We found out the same issue. This is extremely breaking. Makes the generated C# clients useless because MS want it done differently as described by bifa-zuehlke.