可以在同一个.Net 6 WebAPI中使用API Key和JWT Token，但需要对API Key和JWT Token进行分别处理。下面是使用API Key和JWT Token的代码示例：

1. 使用API Key进行身份验证：

在Startup.cs中添加以下代码：

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = "APIKeyScheme";
    options.DefaultChallengeScheme = "APIKeyScheme";
}).AddApiKeySupport(options => {});

services.AddAuthorization(options =>
{
    options.AddPolicy("APIKeyPolicy", policy =>
        policy.RequireAuthenticatedUser().Build());
});

app.UseAuthentication();
app.UseAuthorization();

// 自定义中间件处理API Key验证
app.UseMiddleware(Configuration.GetValue("APIKey"));

创建ApiKeyMiddleware.cs文件，添加以下代码：

public class ApiKeyMiddleware
{
    private readonly RequestDelegate _next;
    private readonly string _apiKey;

    public ApiKeyMiddleware(RequestDelegate next, string apiKey)
    {
        _next = next;
        _apiKey = apiKey;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        if (!context.Request.Headers.TryGetValue("Authorization", out var token)
            || token.ToString() != _apiKey)
        {
            context.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
            await context.Response.WriteAsync("Invalid API Key");
            return;
        }

        await _next(context);
    }
}

2. 使用JWT Token进行身份验证：

在Startup.cs中添加以下代码：

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
}).AddJwtBearer(options =>
{
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidIssuer = Configuration["Jwt:Issuer"],
        ValidAudience = Configuration["Jwt:Audience"],
        IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(Configuration["Jwt:Key"]))
    };
});

services.AddAuthorization(options =>
{
    options.AddPolicy("JwtPolicy", policy =>
        policy.RequireAuthenticatedUser().Build());
});

app.UseAuthentication();
app.UseAuthorization();

在Controller的Action中添加[Authorize(Policy = "JwtPolicy")]属性，