下面是一个使用ASP.NET Core进行索引和搜索JSON文件的示例解决方案：

首先，确保安装了以下NuGet包：

• Microsoft.Extensions.Configuration
• Microsoft.Extensions.Configuration.Json
• Microsoft.Extensions.DependencyInjection
• Microsoft.Extensions.Logging
• Microsoft.Extensions.Logging.Console

在Startup.cs文件中，添加以下代码：

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddLogging(configure => configure.AddConsole())
                .AddTransient()
                .AddSingleton(provider => provider.GetRequiredService());
        
        // 添加其他服务配置
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILoggerFactory loggerFactory)
    {
        // 配置其他中间件和路由
    }
}

然后，创建一个名为JsonFileIndexer.cs的类文件，包含以下代码：

using System.Collections.Generic;
using System.IO;
using Newtonsoft.Json;

public interface IFileIndexer
{
    IEnumerable Search(string searchTerm);
}

public class JsonFileIndexer : IFileIndexer
{
    private readonly List _index;

    public JsonFileIndexer()
    {
        _index = new List();
        IndexJsonFiles("path_to_json_directory"); // 替换为JSON文件所在的目录路径
    }

    public IEnumerable Search(string searchTerm)
    {
        var results = new List();
        foreach (var item in _index)
        {
            if (item.Contains(searchTerm))
            {
                results.Add(item);
            }
        }
        return results;
    }

    private void IndexJsonFiles(string directoryPath)
    {
        foreach (var file in Directory.EnumerateFiles(directoryPath, "*.json", SearchOption.AllDirectories))
        {
            var json = File.ReadAllText(file);
            _index.Add(json);
        }
    }
}

在Controller中，您可以注入IFileIndexer服务并使用它来搜索JSON文件。这里是一个示例控制器方法：

using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("api/[controller]")]
public class SearchController : ControllerBase
{
    private readonly IFileIndexer _fileIndexer;

    public SearchController(IFileIndexer fileIndexer)
    {
        _fileIndexer = fileIndexer;
    }

    [HttpGet("{searchTerm}")]
    public IActionResult Search(string searchTerm)
    {
        var results = _fileIndexer.Search(searchTerm);
        return Ok(results);
    }
}

现在，您可以通过访问/api/search/{searchTerm}来搜索JSON文件。这将返回包含搜索词的JSON文件列表。