如何使用异步等待实现OData核心?

我正在为一个个人项目实施OData。现在我有了这个密码

    [HttpPost]
    [ODataRoute("Classes", RouteName = "PostClass")]
    public IActionResult PostClass([FromBody] Class @class)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }
        @class.Id = Guid.NewGuid();
        _context.Classes.Add(@class);
        _context.SaveChangesAsync();

        //return CreatedAtAction("GetClass", new { id = @class.Id }, @class);
        return Created(@class);
    }

    [HttpPost]
    [ODataRoute("Classes", RouteName = "PostClass")]
    public async Task<ActionResult<Class>> PostClass([FromBody] Class @class)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }
        @class.Id = Guid.NewGuid();
        _context.Classes.Add(@class);
        await _context.SaveChangesAsync();

        return CreatedAtAction("GetClass", new { id = @class.Id }, @class);
        //return Created(@class);
    }

具有

    [HttpPost]
    [ODataRoute("Classes", RouteName = "PostClass")]
    public async Task<ActionResult<Class>> PostClass([FromBody] Class @class)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }
        @class.Id = Guid.NewGuid();
        _context.Classes.Add(@class);
        await _context.SaveChangesAsync();

        //return CreatedAtAction("GetClass", new { id = @class.Id }, @class);
        return Created(@class);
    }

代码无法生成,因为

错误CS0029无法隐式转换类型 到 'Microsoft.AspNetCore.Mvc.ActionResult'Oyg.Api C:\Users\Public\Projects\Oyg server\Api\Controllers\ClassesController.cs 96处于活动状态