自訂 Query Strings 轉換格式

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使用 IValueProviderFactory Interface 自訂 Query Strings 轉換格式

Query Strings 預設格式如 https://localhost:<port>/purchaseorders?purchaseordernumber=PO12345678，此範例說明如何轉換為 SnakeCase，即https://localhost:<port>/purchaseorders?purchase_order_number=PO12345678。

範例

  1. 建立 ASP.NET Core Web API (.NET 8) 專案

  2. 新增 DTO (Data Transfer Object)

    封裝 Query Strings

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    namespace Purchasing.UseCases.Dtos
    {
        public record PurchaseOrderDto(DateTime? StartDate, DateTime? EndDate);
    }

  3. 新增 API Controller

    Response 的部分不影響這個範例，所以省略實作細節。

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    using Microsoft.AspNetCore.Mvc;
    using Purchasing.UseCases.Dtos;

    namespace Purchasing.Api.Controllers
    {
        [Route("[controller]")]
        [ApiController]
        public class PurchaseOrdersController : ControllerBase
        {
            [HttpGet]
            public async Task<IActionResult> ListPurchaseOrdersAsync([FromQuery] PurchaseOrderDto dto)
            {
                // ...
            }
        }
    }

  4. 實作 SnakeCase 的轉換方法

    讀者可以自行實作，在這邊筆者直接參考 Newtonsoft.Json/Utilities/StringUtils.cs。

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    using System.Text;

    namespace Purchasing.Api.ModelBinding
    {
        internal static class SnakeCaseQueryStringValueExtensions
        {
            private enum SeparatedCaseState
            {
                Start,
                Lower,
                Upper,
                NewWord
            }

            internal static string ToSnakeCase(this string s) => ToSeparatedCase(s, '_');

            internal static string ToKebabCase(string s) => ToSeparatedCase(s, '-');

            private static string ToSeparatedCase(string s, char separator)
            {
                if (string.IsNullOrEmpty(s))
                {
                    return s;
                }

                StringBuilder sb = new StringBuilder();
                SeparatedCaseState state = SeparatedCaseState.Start;

                for (int i = 0; i < s.Length; i++)
                {
                    if (s[i] == ' ')
                    {
                        if (state != SeparatedCaseState.Start)
                        {
                            state = SeparatedCaseState.NewWord;
                        }
                    }
                    else if (char.IsUpper(s[i]))
                    {
                        switch (state)
                        {
                            case SeparatedCaseState.Upper:
                                bool hasNext = i + 1 < s.Length;
                                if (i > 0 && hasNext)
                                {
                                    char nextChar = s[i + 1];
                                    if (!char.IsUpper(nextChar) && nextChar != separator)
                                    {
                                        sb.Append(separator);
                                    }
                                }
                                break;
                            case SeparatedCaseState.Lower:
                            case SeparatedCaseState.NewWord:
                                sb.Append(separator);
                                break;
                        }

                        char c;
    #if HAVE_CHAR_TO_LOWER_WITH_CULTURE
                        c = char.ToLower(s[i], CultureInfo.InvariantCulture);
    #else
                        c = char.ToLowerInvariant(s[i]);
    #endif
                        sb.Append(c);

                        state = SeparatedCaseState.Upper;
                    }
                    else if (s[i] == separator)
                    {
                        sb.Append(separator);
                        state = SeparatedCaseState.Start;
                    }
                    else
                    {
                        if (state == SeparatedCaseState.NewWord)
                        {
                            sb.Append(separator);
                        }

                        sb.Append(s[i]);
                        state = SeparatedCaseState.Lower;
                    }
                }

                return sb.ToString();
            }
        }
    }

  5. 新增 SnakeCaseQueryStringValueProvider

    繼承 QueryStringValueProvider，覆寫 GetValue(string key)，把 key 轉換為 SnakeCase ，其中 key 為 DTO 的 Property Name。

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    using Microsoft.AspNetCore.Mvc.ModelBinding;
    using System.Globalization;

    namespace Purchasing.Api.ModelBinding
    {
        internal class SnakeCaseQueryStringValueProvider : QueryStringValueProvider
        {
            public SnakeCaseQueryStringValueProvider(
                BindingSource bindingSource,
                IQueryCollection values,
                CultureInfo? culture)
                : base(bindingSource, values, culture)
            {
            }

            public override ValueProviderResult GetValue(string key)
            {
                return base.GetValue(key.ToSnakeCase());
            }
        }
    }

  6. 新增 SnakeCaseQueryStringValueProviderFactory

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    using Microsoft.AspNetCore.Mvc.ModelBinding;
    using System.Globalization;

    namespace Goldtek.Services.Workflow.Api.ModelBinding
    {
        internal class SnakeCaseQueryStringValueProviderFactory : IValueProviderFactory
        {
            public Task CreateValueProviderAsync(ValueProviderFactoryContext context)
            {
                _ = context ?? throw new ArgumentNullException(nameof(context));

                var query = context.ActionContext.HttpContext.Request.Query;
                if (query?.Count > 0)
                {
                    context.ValueProviders.Add(
                        new SnakeCaseQueryStringValueProvider(
                            BindingSource.Query,
                            query,
                            CultureInfo.CurrentCulture));
                }

                return Task.CompletedTask;
            }
        }
    }

  7. 在 Program.cs 配置 SnakeCaseQueryStringValueProviderFactory

    取代預設的 ValueProviderFactory

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    builder.Services.AddControllers(options =>
    {
        var index = options.ValueProviderFactories.IndexOf(
            options.ValueProviderFactories.OfType<QueryStringValueProviderFactory>()
                .Single());

        options.ValueProviderFactories[index] =
            new SnakeCaseQueryStringValueProviderFactory();
    });

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