ASP.Net MVC, WebAPI, AngularJS - Check if value exists in database - asp.net-mvc

Question

I am using webapi and angularjs in my ASP.net MVC app. Everything is working good but in my insert (post) method I need to check if a value exists in the db before doing an insert. I am not sure where that should go. I ruled out the webapi because a void does not return a value. The logical place seems to be the controller, but I cannot find the right way to call my angular getEmployee(id) method from within the insert controller method. Any help is appreciated.
Angular controller (post):
$scope.insertEmployee = function (employee) {
employeeFactory.insertEmployee(employee)
.success(function (emp) {
$scope.employee = emp;
})
.error(function (error) {
$scope.status = 'Unable to load employee data: ' + error.message;
});
};
Angular factory (post):
factory.insertEmployee = function (employee) {
url = baseAddress + "employee/insert/";
$http.post(url, employee).success(function (data) {
alert("Saved Successfully!!");
}).error(function (data) {
$scope.error = "An Error has occured while saving employee! " + data;
});
};
webapi controller post method:
[Route("api/employee/insert/")]
public void Post(Employee employee)
{
if (ModelState.IsValid)
{
context.Employee.Add(employee);
context.SaveChanges();
}
}
Angular controller (get):
$scope.getEmployees = function (term) {
employeeFactory.getEmployees(term)
.success(function (data) {
$scope.employees = data;
})
.error(function (error) {
$scope.status = 'Unable to load employee data: ' + error.message;
});
};

Answer 1

I would suggest doing this in your web-api server side. You can construct an exception and throw it. Some pseudo-code:
[Route("api/employee/insert/")]
public void Post(Employee employee)
{
if (ModelState.IsValid)
{
// verify doesn't already exist
if(...item-already-exists...) {
var resp = new HttpResponseMessage(HttpStatusCode.Conflict)
{
Content = new StringContent("Employee already exists!")),
ReasonPhrase = "Employee already exists!"
}
throw new HttpResponseException(resp);
}
context.Employee.Add(employee);
context.SaveChanges();
}
}

Answer 2

Your factory doesn't match your controller. If you want to use success and error from employeeFactory.insertEmployee, it needs to return the promise:
factory.insertEmployee = function (employee) {
url = baseAddress + "employee/insert/";
return $http.post(url, employee);
};
So then you can do
employeeFactory.insertEmployee(employee).success( ... )
Now to answer your question you could either do a database read in insertEmployee to check if the value exists before you insert it. Or save a server call and do the check during the insert request: if the employee exists, return an error or a specific message to tell the client.

Answer 3

With the help of floribon and Nicholas Smith I managed to come up with a solution that bubbles the error up to my view, which I display in a div element. This is only bare bones, but is a start.
My angular controller:
$scope.insertEmployee = function (employee) {
employeeFactory.insertEmployee(employee)
.success(function (data) {
$scope.employee = data;
$scope.status = 'The item was saved';
})
.error(function (error) {
$scope.status = 'Unable to save the employee data: ' + error;
});
};
My angular factory:
factory.insertEmployee = function (employee) {
url = baseAddress + "employee/insert/";
return $http.post(url, employee);
};
my webapi controller:
[Route("api/employee/insert/")]
public HttpResponseMessage Post(Employee employee)
{
HttpResponseMessage response;
// check for the employee
var employeeCheck = context.Employee
.Where(b => b.EmployeeNumber == employee.EmployeeNumber)
.FirstOrDefault();
if (employeeCheck == null)
{
// save the item here
response = Request.CreateResponse(HttpStatusCode.OK);
}
else
{
response = Request.CreateResponse(HttpStatusCode.Conflict, "The item already exists");
}
return response;
}
The result is the message is "Unable to save the employee data: The item already exists".