WCF---在 ASP.NET MVC 应用程序中使用 Linq 进行 CRUD 操作？

Question

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First step...Opened WCF created IService :

namespace CRUDOperationWCFMVC
{
    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the interface name "IService1" in both code and config file together.
    [ServiceContract]
    public interface IService1
    {
        [OperationContract]
        bool CreateDetails(EmployeeDetails employeeDetails);
        [OperationContract]
        bool UpdateDetails(EmployeeDetails employeeDetails);
        [OperationContract]
        bool DeleteDetails(int id);
        [OperationContract]
        List<EmployeeDetails> GetDetails();
    }

    public class EmployeeDetails
    {
        [DataMember]
        public int EmpID { get; set; }
        [DataMember]
        public string Name { get; set; }
        [DataMember]
        public string Location { get; set; }
        [DataMember]
        public int? Salary { get; set; }
    }
}

Step 2: then I implemented service code:

public class Service1 : IService1
{
    DataClasses1DataContext dcd = new DataClasses1DataContext();

    public bool CreateDetails(EmployeeDetails employeeDetails)
    {
        Nevint emp = new Nevint();
        emp.EmpID= employeeDetails.EmpID;
        emp.Name = employeeDetails.Name;
        emp.Location = employeeDetails.Location;
        emp.Salary = employeeDetails.Salary;
        dcd.Nevints.InsertOnSubmit(emp);
        dcd.SubmitChanges();
        return true;
    }

    public bool DeleteDetails(int id)
    {
       var delete = (from v in dcd.Nevints where v.EmpID==id select v).FirstOrDefault();
        dcd.Nevints.DeleteOnSubmit(delete);
        dcd.SubmitChanges();
        return true;
    }

    public List<EmployeeDetails> GetDetails()
    {
        List<EmployeeDetails> details = new List<EmployeeDetails>();
        var select= (from v in dcd.Nevints select v);

        foreach (var i in select)
        {
            EmployeeDetails emp = new EmployeeDetails();
            emp.EmpID = i.EmpID;
            emp.Name = i.Name;
            emp.Location = i.Location;
            emp.Salary = i.Salary;
            details.Add(emp);
        }

        return details;
    }

    public bool UpdateDetails(EmployeeDetails employeeDetails)
    {
        var update = (from v in dcd.Nevints.ToList() where employeeDetails.EmpID==v.EmpID select v).FirstOrDefault();
        update.EmpID = employeeDetails.EmpID;
        update.Name = employeeDetails.Name;
        update.Location = employeeDetails.Location;
        update.Salary = employeeDetails.Salary;
        dcd.SubmitChanges();
        return true;
    }
}

Step 3: then I add linq to sql, opened my ASP.NET MVC project for consuming, and added a controller and wrote this code:

namespace ConsumingClient.Controllers
{
    public class EmpdetailsController : Controller
    {
        ServiceReference1.Service1Client serobj=new ServiceReference1.Service1Client();
        ServiceReference1.EmployeeDetails empdetails=new ServiceReference1.EmployeeDetails();
            
        // GET: Empdetails
        public ActionResult Index()
        {
            List<employee> lstemp = new List<employee>();
            var result = serobj.GetDetails();
            foreach (var i in result)
            {
                employee emp = new employee();
                empdetails.EmpID = i.EmpID;
                empdetails.Name = i.Name;
                empdetails.Location = i.Location;
                empdetails.Salary = i.Salary;
                lstemp.Add(emp);
            }
            return View(result);
        }

        // GET: Empdetails/Details/5
        public ActionResult Details(int id)
        {
           Employees emp = new Employees();
            
            return View();
        }

        // GET: Empdetails/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Empdetails/Create
        [HttpPost]
        public ActionResult Create(Employees employees)
        {
            try
            {
                // TODO: Add insert logic here
                empdetails.EmpID=employees.EmpID;
                empdetails.Name = employees.Name;
                empdetails.Location = employees.Location;
                empdetails.Salary = employees.Salary;
                serobj.CreateDetails(empdetails);
                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }

        // GET: Empdetails/Edit/5
        public ActionResult Edit(int id)
        {
            Employees emp = new Employees();
            var result = serobj.GetDetails().FirstOrDefault(a=>a.EmpID==id);
            emp.EmpID = result.EmpID;
            emp.Name = result.Name;
            emp.Location = result.Location;
            emp.Salary = result.Salary;

            return View(emp);
        }

        // POST: Empdetails/Edit/5
        [HttpPost]
        public ActionResult Edit(Employees employees)
        {
            try
            {
                // TODO: Add update logic here
                empdetails.EmpID = employees.EmpID;
                empdetails.Name = employees.Name;
                empdetails.Location = employees.Location;
                empdetails.Salary = employees.Salary;
                serobj.UpdateDetails(empdetails);
                return RedirectToAction("Index");
                
            }
            catch
            {
                return View(employees);
            }
        }

        // GET: Empdetails/Delete/5
        public ActionResult Delete(int id)
        {
            Employees emp = new Employees();
            var result = serobj.GetDetails().FirstOrDefault(a=>a.EmpID==id);
            
            emp.EmpID = result.EmpID;
            emp.Name = result.Name;
            emp.Location = result.Location;
            emp.Salary = result.Salary;

            return View(emp);
        }

        // POST: Empdetails/Delete/5
        [HttpPost]
        public ActionResult Delete(int id, FormCollection collection)
        {
            try
            {
                // TODO: Add delete logic here
                serobj.DeleteDetails(id);
                return RedirectToAction("Index");
            }
            catch
            {
                return View(id);
            }
        }
    }
}

Data was displaying fine. I can create data.

However, when I click on edit and delete, I'm getting an error:

ERROR Message "Server Error in '/' Application.

The parameters dictionary contains a null entry for parameter 'id' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ActionResult Edit(Int32)' in 'ConsumingClient.Controllers.EmpdetailsController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.

Parameter name: parameters

Answer 1

This error is thrown if you attempt to call this controller action and you do not specify the id either in the path portion or as query string parameter. Since your controller action takes an id as parameter you should make sure that you always specify this parameter.

Make sure that when you are requesting this action you have specified a valid id in the url:

http://example.com/somecontroller/Edit/123

If you are generating an anchor, make sure there's an id:

@Html.ActionLink("Edit", "somecontroller", new { id = "123" })

If you are sending an AJAX request, also make sure that the id is present in the url.

If on the other hand the parameter is optional, you could make it a nullable integer:

public ActionResult Edit(int? id)

but in this case you will have to handle the case where the parameter value is not specified. https://coderedirect.com/questions/197477/mvc-the-parameters-dictionary-contains-a-null-entry-for-parameter-k-of-non-n