javascript - 获取Controller的返回值给javascript

Question

我想要的是，我想检查数据库中是否有文件。为此，我在 Controller 中有一个方法来检查这一点并返回相应情况的 bool 值。它看起来像这样:

public bool fileInDb(int empId)
    {
        using (SLADbContext db = new SLADbContext())
        {
            bool file = db.CompetenceUploads.Any(x => x.EmployeeId == empId);
            if (file)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
    }  

我只是检查是否有任何文件分配给给定的员工。

现在我想从 View 中的 javascript 调用此方法，并获取返回值，以便我可以让用户知道是否有文件分配给所选员工。它可能看起来像这样:

$("#get-file").click(function() {

        empId: $("#EmployeeSelect").val();
        var fileInDb = // Get the return value from the method 'fileInDb'

        if(fileInDb) {
            // Let the user download the file he/she requested
            var url = "@Url.Action("GetUploadedFile", "Competence")";
            this.href = url + '?empId=' + encodeURIComponent($("#EmployeeSelect").val());
        } else {
            alert("There is no file assigned to this employee.");
        }
    });  

所以我现在的问题是，如何从 Controller 中的方法获取返回值？

Answer 1

我建议在这里进行一些更改:

更改您的controller方法，使return类型为ActionResult或JsonResult，我更喜欢JsonResult 在这里就足够了，从 controller 重新运行 Json 响应，并使用 $.get 操作此方法。 。您还需要将参数更改为 string，因为 parameter 将以 Json string 形式接收。

public JsonResult fileInDb(string eId) //change signature to string and then convert to int 
{
    int empId=Convert.ToInt32(eId);
    using (SLADbContext db = new SLADbContext())
    {
         bool file = db.CompetenceUploads.Any(x => x.EmployeeId == empId);
         if (file)
         {
             return Json(new { result = true },JsonRequestBehavior.AllowGet);
         }
         else
         {
             return Json(new { result = false},JsonRequestBehavior.AllowGet);
         }
    }
}  

现在您的 ajax-get 调用如下:

$("#get-file").click(function() {
   var eId= $("#EmployeeSelect").val();
   $.get('/YourControllerName/fileInDb',{'eId':eId},function(response){
       //you just need to get the response so $.get is enough to manipulate
       //this will be called once you get the response from controller, typically a callback
       if(response.result) //same result variable we are returning from controller.
       {
            // Let the user download the file he/she requested
            var url = "@Url.Action("GetUploadedFile", "Competence")";
            this.href = url + '?empId=' + encodeURIComponent($("#EmployeeSelect").val());
       } else {
            alert("There is no file assigned to this employee.");
       }
   })
});