Ajax似乎不能在ASP.NET核心中工作

[ApiController]
[Route("api/[controller]")]
public class DataController : ControllerBase
{
    [HttpGet("example")]
    public IActionResult GetExampleData()
    {
        var data = new { Message = "Hello from server!" };
        return Ok(data);
    }
}

document.getElementById('fetchButton').addEventListener('click', function() {
    fetch('/api/data/example')
        .then(response => response.json())
        .then(data => {
            document.getElementById('result').innerText = data.Message;
        })
        .catch(error => console.error('Error:', error));
});

<button id="fetchButton">Fetch Data</button>
<div id="result"></div>

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy("AllowSpecificOrigin",
            builder => builder.WithOrigins("http://example.com"));
    });

    services.AddControllers();
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseCors("AllowSpecificOrigin");

    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseRouting();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}