I am using a Asp.Net MVC application.
In the following code how can I avoid the two database calls for populating a dropdown?
[HttpGet]
public ActionList Upload(){
// do something
//For populating drop downlist take data from db
Return View("Upload");
}
[HttpPost]
public ActionList Upload(){
//do something
//again take data from db for populating dropdown
Return View("Upload");
}
Any other way than jQuery ajax method? Thanks
It depends on the size of the data and how often it's likely to change, but a common solution is just to use the HttpContext's Cache property.
public List<items> GetDropdownlistItems()
{
string cacheKey = "dropdownlistItems";
if (HttpContext.Current.Cache[cacheKey] != null)
{
return (List<items>)HttpContext.Current.Cache[cacheKey];
}
var items = GetItemsFromDatabase();
HttpContext.Current.Cache.Insert(cacheKey, items, null, DateTime.Now.AddHours(1), System.Web.Caching.Cache.NoSlidingExpiration);
return items;
}
I tend to cache data that is rarely changed such as this.
Checkout EntLibs Caching Application Blocks.
You can load all data into the cache on first use, and set an expiry time depending on how quickly you want changes in the db to be made effective.
Basically, add a layer between your Controller and the Database, that runs code something like this:
MyData myData = null;
myData = (MyData )cacheManager.GetData("myData");
if (myData == null)
{
myData = dataProvider.GetData();
cacheManager.Add("myData", myData, CacheItemPriority.Normal, null, timeToExpire);
}
return myData;
Where myData is the data you need for a dropdown.
Related
Total beginner here. I am having problems displaying data from the database. The code below fetches the data from the row with "id" successfully.
Public IActionResult Item(int id)
{
var ItemInDb = _context.Items.Find(id);
if(ItemInDb == null)
{
return NotFound();
}
return View(ItemInDb);
}
However, I can not find the simple way to display this data in corresponding view. Any help is appreciated.
this variable works fine if used by one user, but when used by two or more users then the "static" variable will be read by the next user, the first user instance when filling the gridview there are 5 rows of data and I try to access through other browser when entering the page, gridview on the second user already filled 5 rows of data in input by the first user. then how the solution to this problem? please see my code and give me an solutions. thanks.
static List<ServicesModels> _gridPackageDetail = new List<ServicesModels>();
private void AddListAction(string alfa, string beta)
{
ServicesModels data = new ServicesModels()
{
id_service_detail = Guid.NewGuid(),
scope_name = alfa,
detail_name= beta
};
_gridPackageDetail.Add(data);
}
public ActionResult GridPackageDetail()
{
ViewBag.DataListPackage = _gridPackageDetail.OrderBy(a => a.scope_name).ToList();
return PartialView();
}
my code in mvc3 controller.
The code is working fine, because this is what intended by "static", to have the same data for multi users. In your case you need to create a list or dictionary or multi-dimensional array (any data structure you are comfortABLE with) and save the data per use in it, and then retrieve the data when needed based on the user id.
static List<ServicesModels> _gridPackageDetail = new List<ServicesModels>();
private void AddListAction(string alfa, string beta)
{
ServicesModels data = new ServicesModels()
{
id_service_detail = Guid.NewGuid(),
scope_name = alfa,
detail_name= beta,
user_id = getTheID()// Get the id of the user
};
_gridPackageDetail.Add(data);
}
public ActionResult GridPackageDetail()
{
ViewBag.DataListPackage = _gridPackageDetail.OrderBy(a => a.scope_name && user_id ==getTheID()).ToList();
return PartialView();
}
replace getTheID() by your way of getting the id of the user.
This is used if you want to keep the data of all users. else you should remove the static keyword.
I have two GridViews. I've got method GetGeneralDiagnosis which returns a list of all diagnosis:
CODE DIAGNOSIS
F50 Eating disorders
F51 Nonorganic sleep disorders
and method GetSpecificDiagnosis which returns more specific list:
CODE DIAGNOSIS
F50.0 Anorexia nervosa
F50.1 Atypical anorexia nervosa
F51.0 Nonorganic insomnia
F51.1 Nonorganic hypersomnia
Now I've got method which bind SPECIFIC DIAGNOSIS to second GridView according to GENERAL DIAGNOSIS from first GridView.
protected void gvGeneralDiagnosis_SelectedIndexChanged(object sender, EventArgs e)
{
string generalDiagnosis = gvGeneralDiagnosis.DataKeys[gvGeneralDiagnosis.SelectedIndex].Values["ICD10Code"].ToString();
var ICD10 = Visit.GetSpecificDiagnosis(); // here I'm getting data from database
gvSpecificDiagnosis.DataSource = ICD10.Where(i => i.ICD10Code.Contains(generalDiagnosis)).Select(i => new { i.ICD10Name, i.ICD10Code });
gvSpecificDiagnosis.DataBind();
}
I don't want to connect to database each time selected index is changed.
How can i get my list var ICD10 = Visit.GetSpecificDiagnosis() only once? I heard that global variables are very bad idea, so how can I do that in another way?
You can use a private member variable. This one "lives" as long as the class containing it lives. Wrap it with a property to access it and automatically read it from the database, if necessary.
private TypeOfICD10 _icd10;
private TypeOfICD10 ICD10
{
get
{
if (_icd10 == null) { // Get from database.
_icd10 = Visit.GetSpecificDiagnosis();
}
return _icd10;
}
}
Now you can use it like this and it will be read from the db only at the first call
protected void gvGeneralDiagnosis_SelectedIndexChanged(object sender, EventArgs e)
{
string generalDiagnosis = gvGeneralDiagnosis.DataKeys[gvGeneralDiagnosis.SelectedIndex].Values["ICD10Name"].ToString();
gvSpecificDiagnosis.DataSource = ICD10
.Where(i => i.ICD10Code.Contains(generalDiagnosis))
.Select(i => new { i.ICD10Name, i.ICD10Code });
gvSpecificDiagnosis.DataBind();
}
You can have your Visit class cache the returned data.
When GetSpecificDiagnosis is called, it will check whether this data was already retrieved from the database, and return it if it was. If it wasn't, it'll retrieve it from the database and save it to its cache.
One thing you should pay attention to is whether this data is static (i.e. never changes throughout the application's lifetime) or is it dynamic. In the first case, you won't have to do any special handling, but if it's the latter, you'll have to invalidate the cache one the information in the database has changed.
I recommend you to have a look here to see how to get started with caching in ASP.NET.
I don't know much about the Visist class from your question but why not cache ICD10 this way you will be using the cached object and the Database call will made only if the Cache Key ICD10 has a value of null
Example :
if(Cache["ICD10"] == null)
{
var ICD10 = Visit.GetSpecificDiagnosis();
Cache["ICD10"] = ICD10;
}
else
{
var ICD10 = Cache["ICD10"];
}
I'm wanting to capture the old values within a model so I can compare with the new values after submission, and create audit logs of changes a user makes.
My guess is doing it with hidden input boxes with duplicated old value properties would be one way. But wondering if there are any other good alternatives?
Thanks
In the save method, just go and get the original object from the database before saving the changes, then you have your old and new values to compare against? :)
This sounds like standard auditing. You should not worry about what has changed just capture EVERYTHING and who made the change. Unless there is some sort of real time reporting that needs to be done.
Possible auditing implementations:
CQRS, in a nutshell it tracks every change to a given object. The downside is it's an architecture that is more involved to implement.
The Rolling ledger. Each insert is a new row in the database. The most current row is used for display purposes, but with each update, a new row is inserted into the database.
Yet another approach is to save it off into an audit table.
All get the job done.
You could also store the original model in the view bag and do something like this...
// In the controller
public ActionResult DoStuff()
{
// get your model
ViewBag.OriginalModel = YourModel;
return View(YourModel);
}
// In the View
<input type="hidden" name="originalModel" value="#Html.Raw(Json.Encode(ViewBag.OriginalModel));" />
// In the controller's post...
[HttpPost]
public ActionResult DoStuff(YourModel yourModel, string originalModel)
{
// yourModel will be the posted data.
JavaScriptSerializer JSS = new JavaScriptSerializer();
YourModel origModel = JSS.Deserialize<YourModel>(originalModel);
}
I didn't get a chance to test this, just a theory :)
Exactly what mattytommo says is the preferred method all around
Instantiate new view model for creating a new entity
public ActionResult Edit(int id) {
var entity = new Entity(id); // have a constructor in your entity that will populate itself and return the instance of what is in the db
// map entity to ViewModel using whatever means you use
var model = new YourViewModel();
return View(model);
}
Post changes back
[HttpPost]
public ActionResult Edit(YourViewModel model) {
if (ModelState.IsValid) {
var entity = new YourEntity(model.ID); // re-get from db
// make your comparison here
if(model.LastUserID != entity.LastUserID // do whatever
... etc...
}
return View(model);
}
I'm tryping to use JSON to update records in a database without a postback and I'm having trouble implementing it. This is my first time doing this so I would appreciate being pointed in the right direction.
(Explanation, irrelevant to my question: I am displaying a list of items that are sortable using a jquery plugin. The text of the items can be edited too. When people click submit I want their records to be updated. Functionality will be very similar to this.).
This javascript function creates an array of the objects. I just don't know what to do with them afterwards. It is called by the button's onClick event.
function SaveLinks() {
var list = document.getElementById('sortable1');
var links = [];
for (var i = 0; i < list.childNodes.length; i++) {
var link = {};
link.id = list.childNodes[i].childNodes[0].innerText;
link.title = list.childNodes[i].childNodes[1].innerText;
link.description = list.childNodes[i].childNodes[2].innerText;
link.url = list.childNodes[i].childNodes[3].innerText;
links.push(link);
}
//This is where I don't know what to do with my array.
}
I am trying to get this to call an update method that will persist the information to the database. Here is my codebehind function that will be called from the javascript.
public void SaveList(object o )
{
//cast and process, I assume
}
Any help is appreciated!
I have recently done this. I'm using MVC though it shouldn't be too different.
It's not vital but I find it helpful to create the contracts in JS on the client side and in C# on the server side so you can be sure of your interface.
Here's a bit of sample Javascript (with the jQuery library):
var item = new Item();
item.id = 1;
item.name = 2;
$.post("Item/Save", $.toJSON(item), function(data, testStatus) {
/*User can be notified that the item was saved successfully*/
window.location.reload();
}, "text");
In the above case I am expecting text back from the server but this can be XML, HTML or more JSON.
The server code is something like this:
public ActionResult Save()
{
string json = Request.Form[0];
var serializer = new DataContractJsonSerializer(typeof(JsonItem));
var memoryStream = new MemoryStream(Encoding.Unicode.GetBytes(json));
JsonItem item = (JsonItem)serializer.ReadObject(memoryStream);
memoryStream.Close();
SaveItem(item);
return Content("success");
}
Hope this makes sense.
You don't use CodeBehind for this, you use a new action.
Your action will take an argument which can be materialized from your posted data (which, in your case, is a JavaScript object, not JSON). So you'll need a type like:
public class Link
{
public int? Id { get; set; }
public string Title { get; set; }
public string Description { get; set; }
public string Url { get; set; }
}
Note the nullable int. If you have non-nullable types in your edit models, binding will fail if the user does not submit a value for that property. Using nullable types allows you to detect the null in your controller and give the user an informative message instead of just returning null for the whole model.
Now you add an action:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult DoStuff(IEnumerable<Link> saveList)
{
Repository.SaveLinks(saveList);
return Json(true);
}
Change your JS object to a form that MVC's DefaultModelBinder will understand:
var links = {};
for (var i = 0; i < list.childNodes.length; i++) {
links["id[" + i + "]"] = list.childNodes[i].childNodes[0].innerText;
links["title[" + i + "]"] = list.childNodes[i].childNodes[1].innerText;
links["description[" + i + "]"] = list.childNodes[i].childNodes[2].innerText;
links["url[" + i + "]"] = list.childNodes[i].childNodes[3].innerText;
}
Finally, call the action in your JS:
//This is where I don't know what to do with my array. Now you do!
// presumes jQuery -- this is much easier with jQuery
$.post("/path/to/DoStuff", links, function() {
// success!
},
'json');
Unfortunately, JavaScript does not have a built-in function for serializing a structure to JSON. So if you want to POST some JSON in an Ajax query, you'll either have to munge the string yourself or use a third-party serializer. (jQuery has a a plugin or two that does it, for example.)
That said, you usually don't need to send JSON to the HTTP server to process it. You can simply use an Ajax POST request and encode the form the usual way (application/x-www-form-urlencoded).
You can't send structured data like nested arrays this way, but you might be able to get away with naming the fields in your links structure with a counter. (links.id_1, links.id_2, etc.)
If you do that, then with something like jQuery it's as simple as
jQuery.post( '/foo/yourapp', links, function() { alert 'posted stuff' } );
Then you would have to restructure the data on the server side.