Say for example if I have a business entity -> Customer, which has customerId, customerName and customerType. I have created an asp:Hidden Variable hdnCustomer to runat="server"
If I wanted to serialize the value of the customer business entity (in the code behind) to the hdnCustomer then how would I do that? Also once serialized how would I deserialize it?
// Pseudo code
Collection<Customer> customerList = new Collection<Customer>();
customerList = BusinessAccess.GetCustomerList();
hdnCustomer = serialize and assign the value of 'customerList' to hdnCustomer;
...
...
// Later on a select index change of one of the drop down lists
Inside the event handler for the drop down list:
{
Collection<Customer> customerList = new Collection<Customer>();
customerList = deserialize the value from hdnCustomer
int a = Convert.ToInt32(ddlDropDown.SelectedValue);
foreach(a in customerList)
{
// Do something
}
}
You can serialise to and from XML using XmlSerializer:
http://support.microsoft.com/kb/815813
However, if you just store the object in the ViewState[] collection that should work better:
ViewState["Customer"] = customerList;
It does the same thing: store the serialisable object in the page, hidden from the user: but it won't be in a human-readable format.
(edit: To deserialise, just get the value of ViewState["Customer"], checking for a null before using it!)
edit 2: a useful link about storing objects in ViewState:
http://www.beansoftware.com/ASP.NET-Tutorials/ViewState-In-ASP.NET.aspx
Hope that helps.
I think .net has already providing some classes to do so, look at this example
Related
I'd like to store several different object types in a single Cosmos DB container, as they are all logically grouped and make sense to read together by timestamp to avoid extra HTTP calls.
However, the Cosmos DB client API doesn't seem to provide an easy way of doing the reads with multiple types. The best solution I've found so far is to write your own CosmosSerializer and JsonConverter, but that feels clunky: https://thomaslevesque.com/2019/10/15/handling-type-hierarchies-in-cosmos-db-part-2/
Is there a more graceful way to read items of different types to a shared base class so I can cast them later, or do I have to take the hit?
Thanks!
The way I do this is to create the ItemQueryIterator and FeedResponse objects as dynamic and initially read them untyped so I can inspect a "type" property that tells me what type of object to deserialize into.
In this example I have a single container that contains both my customer data as well as all their sales orders. The code looks like this.
string sql = "SELECT * from c WHERE c.customerId = #customerId";
FeedIterator<dynamic> resultSet = container.GetItemQueryIterator<dynamic>(
new QueryDefinition(sql)
.WithParameter("#customerId", customerId),
requestOptions: new QueryRequestOptions
{
PartitionKey = new PartitionKey(customerId)
});
CustomerV4 customer = new CustomerV4();
List<SalesOrder> orders = new List<SalesOrder>();
while (resultSet.HasMoreResults)
{
//dynamic response. Deserialize into POCO's based upon "type" property
FeedResponse<dynamic> response = await resultSet.ReadNextAsync();
foreach (var item in response)
{
if (item.type == "customer")
{
customer = JsonConvert.DeserializeObject<CustomerV4>(item.ToString());
}
else if (item.type == "salesOrder")
{
orders.Add(JsonConvert.DeserializeObject<SalesOrder>(item.ToString()));
}
}
}
Update:
You do not have to use dynamic types if want to create a "base document" class and then derive from that. Deserialize into the documentBase class, then check the type property check which class to deserialize the payload into.
You can also extend this pattern when you evolve your data models over time with a docVersion property.
I need some clarity about session and how to add objects, because I think I do it the wrong way.
First I create a session to hold a list of Products:
Session["ShoppingCart"] = new List<Products>();
To add Products to the list, I do like this:
Session["ShoppingCart"] = new Products { ID = productId, Name = name };
I guess this isn't the right way?
I guess this isn't the right way?
Yes, this isn't the right way (please skip towards the last paragraph of my answer to know the correct way - which is not to use ASP.NET session at all). The correct way is to first get the object you stored inside the session by trying it to cast it to the same .NET type yo uhave stored inside the session:
var products = Session["ShoppingCart"] as List<Products>;
and then if this item is not null add the corresponding product to the list. We should of course make the necessary type check that the session actually contained a value with the specified key and that this value is of the expected type:
if (products != null)
{
var product = new Products { ID = productId, Name = name };
products.Add(product);
}
Of course we are using object references here which will only work if you are storing your session in-memory (sessionState mode = InProc) which of course is absolutely a terrible disaster and something you should never do in production. In a production environment you are probably persisting your session in a session server or even SQL server, aren't you? In this case it is more than obvious that working with object references is a recipe for disaster. So in this case once you have added the new product to the session you should of course set back the new list value to the session which will serialize the object instance to the corresponding data store:
if (products != null)
{
var product = new Products { ID = productId, Name = name };
products.Add(product);
Session["ShoppingCart"] = products;
}
Now, after all this being said I must admit that using ASP.NET Session is probably the huge mistake you would ever commit in a real world application. So basically every time you are using Session["xxx"] you are doing it wrong. Simply search the entire solution for the Session keyword and just get rid of it.
In order to add itens to an existing list on the Session, you must first retrieve the list then add the object to it. Here's an example:
Session["ShoppingCart"] = new List<Products>();
List<Products> productsList = (List<Products>)Session["ShoppingCart"];
productsList.add(new Products { ID = productId, Name = name });
Session["ShoppingCart"] = productsList;
i am new to .net..i have to develop an asp.net application.
The UI of the web page will have a Data-bound Grid control on the Home page and there will be a Textbox where users can enter their search criteria.
I know to do this by using ado.net concept...
But i am supposed to do it using generics concept.How can i store the values in the generic list or dictionary of .net and filter the data based on the text entered in the text box.
Please help me out..
Thanks in advance..
You can indeed bind a GridView to List<T>, I do it all the time, like this:
Create a POCO for the data
public class SomeData
{
public string SomeField {get;set;}
public string SomeOtherField {get;set;}
}
Build the list (either manually or as a result a DB query) e.g.
var mylist = new List<SomeData>();
var myitem = new SomeData()
{
SomeField = "Hello",
SomeOtherField = "World"
};
To Filter the data do something like this:
myfilter = MyTextBox.Value;
mylist = mylist.Where(somedata => somedata.SomeField.Equals(myfiltervalue)).ToList();
Bind it to the GridView
mygridview.DataSource = mylist;
mygridview.DataBind();
And this is it!!
I assume you know ado.net and how to bind gridview.
You just need to iterate through your database resultset and add it to list and bind it.
Following link might help you to begin with:
http://www.aspsnippets.com/Articles/How-to-bind-GridView-with-Generic-List-in-ASPNet-using-C-and-VBNet.aspx
Pass your textbox value to your database query/stored procedure as parameter and return the result based on search value.
Edit:
You may want to use FindAll, Find method.
Check below link:
http://msdn.microsoft.com/en-us/library/aa701359(VS.80).aspx
i want to make sure all product names are unique so i tried to do the following.
but it is causing an infinity loop at the lambda expression.
public partial class Product
{
partial void OnProductNameChanging(string value)
{
using(var ctx = new MyEntityContext()){
var val = value;
var item = ctx.Products.Where(o=>o.ProductName == val).FirstOrDefault();
if(item != null)
throw new ValidationException("Product Name existed.");
}
}
}
i'm using asp.net 4.0 with dynamic data and entity framework.
Why don't you set it up on database level and handle exeption in case if product name already exists?
I am not too familiar with EF, but you should get the changeset and compare values. That is, for the Product Entity and in the case of the the changeset having an Update, compare the EXISTING value with NEW, and change the new in the case of duplication.
Here's how to get changeSet in EF :
http://davidhayden.com/blog/dave/archive/2005/11/16/2570.aspx
the comparison and value must be called before any context.SubmitChanges();
Hope this helps.
My problem is that I am trying to return a simple query that contains an object Story. The Story object has a UserId in the table which links to aspnet_users' UserId column. I have created a partial class for Story that adds the UserName property since it does not exist in the table itself.
The following query gets all stories; however, a pagination helper takes the query and returns only what's necessary once this is passed back to the controller.
public IQueryable<Story> FindAllStories(){
var stories = (from s in db.Stories
orderby s.DateEntered descending
select new Story
{
Title = s.Title,
StoryContent = s.StoryContent,
DateEntered = s.DateEntered,
DateUpdated = s.DateUpdated,
UserName = s.aspnet_User.UserName
}
);
return stories;
}
When the helper does a .count() on the source it bombs with the following exception:
"Explicit construction of entity type 'MyWebsite.Models.Story' in query is not allowed."
Any ideas? It's not a problem with the helper because I had this working when I simply had the UserName inside the Story table. And on a side note - any book recommendations for getting up to speed on LINQ to SQL? It's really kicking my butt. Thanks.
The problem is precisely what it tells you: you're not allowed to use new Story as the result of your query. Use an anonymous type instead (by omitting Story after new). If you still want Story, you can remap it later in LINQ to Objects:
var stories = from s in db.Stories
orderby s.DateEntered descending
select new
{
Title = s.Title,
StoryContent = s.StoryContent,
DateEntered = s.DateEntered,
DateUpdated = s.DateUpdated,
UserName = s.aspnet_User.UserName
};
stories = from s in stories.AsEnumerable() // L2O
select new Story
{
Title = s.Title,
StoryContent = s.StoryContent,
...
};
If you really need to return an IQueryable from your method and still need the Username of the user you can use DataContext.LoadOptions to eagerload your aspnet_user objects.
See this example.