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
Related
So I have the code code which binds the object class to a list box:
lstDealers.DataSource = dealers;
lstDealers.DataTextField = "DealerName";
lstDealers.DataBind();
This works fine, I have no problem displaying the values. However the problem I am having is I am trying to get the class from the list object.
I have tried two different methods but none have worked:
var selectedItems = from ListItem i in lstDealers.Items where i.Selected select i;
Dealer dealer = (Dealer)selectedItems;
and
Dealer dealer = (Dealer)lstDealers.SelectedItem;
Now I know the second one works in a winform, however I am trying to accomplish this in ASP.Net framework 4.5
Any suggestions?
In web forms the SelectedItem does not have the object of type being assigned in DataSource rather you will get ListItem.
You have to use the current item to get the record from your data source as the dealers object is not available on postback. You can assign unique id to DataValueField which you will use after postback to fetch the record from datasource (database)
lstDealers.DataValueField = "IdOfDealer";
On postback
string dealerId = (Dealer)lstDealers.SelectedValue;
Dealer dealer = someMethodToFetchAndReturnDealer(dealerId);
this is my first post, hopefully I'm following the rules!
After a few weeks of banging my head against brick walls and endless hours of internet searches, I have decided I need to make my own post and hopefully find the answers and guidance from all you experts.
I am building an ASP.NET application (in Visual Studio 2010) which uses an SQL 2008 database and Entity Framework 4 to join the two parts together. I designed the database as a database project first, then built the Entity Model as a class project which is then referenced in the main ASP.NET project. I believe this is called Database First in Entity Framwork terms?
I'm fairly new to Web Apps (I mainly develop WinForms apps) and this is my first attempt at using Entity Framwork.
I can just about understand C# so any code samples or snippets you might supply would be preferred in VB if possible.
To give some background on where I am so far. I built a regsitration page called register.aspx and created a wizard style form using ASP:Wizard with ASP:TextBox, ASP:DropdownList and ASP:CheckBoxList it's all laid out inside a HTML table and uses CSS for some of the formatting. Once the user gets the the last page in the wizard and presses "Finish" I execute some code in the VB code behind file as follows:
Protected Sub wizardRegister_FinishButtonClick(sender As Object, e As System.Web.UI.WebControls.WizardNavigationEventArgs) Handles wizardRegister.FinishButtonClick
Dim context As New CPMModel.CPMEntities
Dim person As New CPMModel.Person
Dim employee As New CPMModel.Employee
Dim newID As Guid = Guid.NewGuid
With person
.ID = newID
.UserID = txbx_UserName.Text
.Title = ddl_Title.SelectedValue
.FirstName = txbx_FirstName.Text
.MiddleInitial = txbx_MiddleInitial.Text
.FamilyName = txbx_FamilyName.Text
.Gender = ddl_Gender.SelectedValue
.DOB = txbx_DOB.Text
.RegistrationDate = Date.Now
.RegistrationMethod = "W"
.ContactMethodID = New Guid(ddl_ContactMethodList.SelectedValue)
.UserName = txbx_UserName.Text
If Not (My.Settings.AuthenticationUsingAD) Then
.Password = txbx_Password.Text ' [todo] write call to salted password hash function
End If
.IsRedundant = False
.IsLocked = False
End With
context.AddToPeople(person)
With employee
.ID = newID
.PayrollNumber = txbx_PayrollNumber.Text
.JobTitle = txbx_JobTitle.Text
.DepartmentID = ddl_DepartmentList.SelectedValue
.OfficeNumber = txbx_OfficeNumber.Text
.HomeNumber = txbx_HomeNumber.Text
.MobileNumber = txbx_MobileNumber.Text
.BleepNumber = txbx_BleepNumber.Text
.OfficeEmail = txbx_OfficeEmail.Text
.HomeEmail = txbx_HomeEmail.Text
.IsRedundant = False
.RedundantDate = Nothing
'--------------------------
.FiledBy = Threading.Thread.CurrentPrincipal.Identity.Name
.FiledLocation = My.Computer.Name
.FiledDateTimeStamp = Date.Now
'----------------------------
End With
context.AddToEmployees(employee)
context.SaveChanges()
End Sub
The above works fine, seemed to be a sensible way of doing it (remember I'm new to Entity Framework) and gave me the results I extpected.
I have another page called manage.aspx on this page is a tab control, each tab page contains a asp:DetailsView which is bound to an asp:EntityDataSource, I have enabled Update on all the Entity Data Sources and on some I have also enabled Insert, none of the have delete enabled.
If I build and run the app at this stage everything works fine, you can press the "edit" link make changes and then press "update" and sure enough those updates are displayed on the screen instantly and the database does have the correct values in.
Here's the problem, I need to intercept the update in the above code (the bold bit) notice there is a column in my database called FiledBy, FiledLocation, and FiledDateTimeStamp. I don't want to show these columns to the user viewing the ASP.NET page but I want to update them when the user presses update (if there were any changes made). I have tried converting the ASP:DetailsView into a template and then coding the HTML side with things like;
<## Eval(User.Name) #>
I did manage to get it to put the correct values in the textboxes when in edit mode but I had the following problems;
It didn't save to the database
I have to show the textboxes which I don't want to do
I have read on several other posts on here and other websites that you can override the SaveChanges part of the Entity Framwork model one example of this is in the code below;
public override int SaveChanges()
{
var entities = ChangeTracker.Entries<YourEntityType>()
.Where(e => e.State == EntityState.Added)
.Select(e => e.Entity);
var currentDate = DateTime.Now;
foreach(var entity in entities)
{
entity.Date = currentDate;
}
return base.SaveChanges();
}
The problem is, that whilst I understand the idea, and can just about transalate it to VB I have no idea how to implement this. Where do I put the code? How do I call the code? etc.
I would ideally like to find a solution that meets the following requirements:
Doesn't get overwritten if I was to regenerate / update the Entity Model
Doesn't need to be copy and pasted for every table in my model (most but not all have the audit columns in)
Can be used for other columns, for example, if a user make a selection in a check list I may want to write some value into another (not exposed to the user) column.
Am I taking the right approach to displaying data in may webpages I certainly find the DataView and GridView limiting, I did think about creating a form like the registration form in table tags but have no Idea how to populate the textboxes etc with values from the database nor how to implement paging as many of the tables have one to many relationships, although saving changes would be easy if I did populate textboxes on a table.
Thank you all in advance to anyone who offers there support.
Kevin.
Ok so I have now got closer, but still not got it working correctly. I've used the following code to edit the value in the DetailsView on the Databound event. If writes the correct timestamp into the read only textbox but does not right this value back to the database when you press the Update button on the DetailsView control.
Protected Sub dv_Employee_DataBound(sender As Object, e As EventArgs) Handles dv_Employee.DataBound
If dv_Employee.CurrentMode = DetailsViewMode.Edit Then
For Each row In dv_Employee.Rows
If row.Cells(0).Text = "FiledDateTimeStamp" Then
row.Cells(1).Text = Date.Now()
End If
Next
End If
End Sub
I like the idea of overriding the save changes method. Your context should be a partial class, so you just need to define another class marked as partial with the same name in the same namespace and add the override to it.
Namespace CPMModel
Partial Public Class CPMEntities
...Your override here
End Class
Since this is an override of the default SaveChanges method you do not need to make any changes in how it is called. You will need to find a way to gain access to entity level properties.
Since this is the method that commits changes for all entities you will not be able to access the properties like you do in your example, since the entity class does not define an of your concrete properties. So you need to create partial classes for your entities and have them all implement an interface that defines the properties you would like to interact with.
Create interface:
Interface IDate
Property Date() as DateTime
End Interface
Create partial class for each of your entities that implements the IDate interface. (The same rules apply for these partial classes they must be marked partial, have the same name as the class they extend and live in the same namespace) Then in your SaveChanges override
public override int SaveChanges()
{
var entities = ChangeTracker.Entries<Entity>()
.Where(e => e.State == EntityState.Added)
.Select(e => e.Entity);
var currentDate = DateTime.Now;
foreach(var entity in entities)
{
***Now cast entity to type of IDate and set your value ***
entity.Date = currentDate;
}
return base.SaveChanges();
}
I don't write in Vb so I left the syntax in C#.
That should fulfill all of your requirements.
Ok, so this isn't exactly how I imagined it would work but it has infact met my needs. Kind of!
What I did was Write a Protected Sub in the code behind file of the aspx file.
Protected Sub CustomEntityUpdate_Employee(sender As Object, e As
EntityDataSourceChangingEventArgs)
Dim emp As CPMModel.Employee = e.Entity
' Check if the entity state is modified and update auditing columns
If emp.EntityState = EntityState.Modified Then
emp.FiledDateTimeStamp = Date.Now()
emp.FiledBy = Threading.Thread.CurrentPrincipal.Identity.Name
emp.FiledLocation = My.Computer.Name
End If
End Sub
Then in the aspx page I edited the Entity datasource code to call the above sub routine
#nUpdating="CustomEntityUpdate_Employee"
<asp:EntityDataSource
ID="eds_Employee"
runat="server"
ConnectionString="name=CPMEntities"
DefaultContainerName="CPMEntities"
EnableFlattening="False"
EnableUpdate="True"
EntitySetName="Employees"
AutoGenerateWhereClause="True"
Where=""
EntityTypeFilter="Employee"
**OnUpdating="CustomEntityUpdate_Employee">**
<WhereParameters>
<asp:SessionParameter
Name="ID"
SessionField="UserID" />
</WhereParameters>
</asp:EntityDataSource>
The Protected Sub, checks if the entity has been modified and if it has updates the entity auditing columns with the values I wanted.
It works but it will certainly make for a lot more code, I ideally would like a way to package this up perhaps into a class and just call the sub from the various aspx pages via the OnUpdating event and have the class figure out which entity was making the call and handle all the logic there.
hi
I've developed an application using strong-typed dataset with .net framework 3.5.
is there a way to change the source table for a tableadapter programmatically?
thnx
There are a couple of ways that you can do this. First you could just add a new query that pulls from the different table, and then execute the method for that query, as long as the columns match it will work.
If you need to dynamically change the one of the statements you can access the command collection of the table adapter, it is protected though, so the easiest way to do this is to create a partial class to extend the one generated by the designer. Once you do this you can add your own method to return the data. You can use adapter.CommandCollection[0].CommandText to get and set the SQL for the the default GetData command that is created.
Once you do this you can change it, clear out the parameters, add new parameters or whatever you want to do, then you set the CommandText with the altered SQL, and call GetData or whatever you named the command and it will execute and return as usual.
Here is a code example:
using System.Data.SqlClient;
namespace DataTableAdapters
{
public partial class Data_ItemTableAdapter
{
public Data.Data_ItemDataTable GetDynamicExample(string SearchValue)
{
using (Data_ItemTableAdapter a = new Data_ItemTableAdapter())
{
SqlCommand cmd = a.CommandCollection[0];
cmd.Parameters.Clear();
string SQL = #"Select Data_Item_ID, Data from Data_Item where
SearchValue = #SearchValue";
cmd.CommandText = SQL;
cmd.Parameters.AddWithValue("#SearchValue", SearchValue);
return a.GetData();
}
}
}
}
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
I have this really random problem with is bugging me. It works at the end of the day but the problem took some time to figure out and was wondering why this happens so if anyone shed some light on the subject I would be really grateful. Here is the problem
I have the following two columns on my datagrid
<asp:boundcolumn
datafield="contentsection.Id"
headerstyle-cssclass="dgHead"
headertext="Section"
itemstyle-cssclass="dgItem" />
and
<asp:templatecolumn>
<itemtemplate><%#Eval("contentsection.Id") %></itemtemplate>
</asp:templatecolumn>
The first column gives me the error of:
A field or property with the name 'contentsection.Id' was not found on the selected data source
but the second on runs fine. Any ideas or theories as to why this is happening ?
The way that I call and bind my data is like so:
Page Load Code Behind
ContentList.DataSource = ContentBlockManager.GetList();
ContentList.DataBind();
The GetList() function it is overloaded and by default passed a 0
public static List<ContentBlockMini> GetList(int SectionId)
{
List<ContentBlockMini> myList = null;
SqlParameter[] parameters = { new SqlParameter("#ContentSectionId", SectionId) };
using (DataTableReader DataReader = DataAccess.GetDataTableReader("dbo.contentblock_get", parameters))
{
if (DataReader.HasRows)
{
myList = new List<ContentBlockMini>();
}
while (DataReader.Read())
{
myList.Add(FillMiniDataRecord(DataReader));
}
}
return myList;
}
and my filling of the data record. The ContentSection is another Object Which is a property of the ContentBlock object
private static ContentBlockMini FillMiniDataRecord(IDataRecord DataRecord)
{
ContentBlockMini contentblock = new ContentBlockMini();
contentblock.Id = DataRecord.GetInt32(DataRecord.GetOrdinal("Id"));
contentblock.Name = DataRecord.GetString(DataRecord.GetOrdinal("Name"));
contentblock.SEOKeywords = DataRecord.IsDBNull(DataRecord.GetOrdinal("SEOKeywords")) ? string.Empty : DataRecord.GetString(DataRecord.GetOrdinal("SEOKeywords"));
contentblock.SEODescription = DataRecord.IsDBNull(DataRecord.GetOrdinal("SEODescription")) ? string.Empty : DataRecord.GetString(DataRecord.GetOrdinal("SEODescription"));
if (DataRecord.GetInt32(DataRecord.GetOrdinal("ContentSectionId")) > 0)
{
ContentSection cs = new ContentSection();
cs.Id = DataRecord.GetInt32(DataRecord.GetOrdinal("ContentSectionId"));
cs.Name = DataRecord.IsDBNull(DataRecord.GetOrdinal("ContentSectionName")) ? string.Empty : DataRecord.GetString(DataRecord.GetOrdinal("ContentSectionName"));
contentblock.contentsection = cs;
}
return contentblock;
}
There you go that is pretty much the start to end.
Databinding can only access "top level" properties on an object. For example, if my object is
Company with simple properties CompanyId and Name and a child object for Address, databinding can only access CompanyId and Name, not Company.Address.City.
Eval can access child object properties if you import the namespace using an #Import page directive.
The "Bind" marker is a two-way bind and is made using the default namespace attached to the datasource of the object. This can't be overridden, and because of this tightly coupled connection the namespace should be left off as assumed (since it's dynamically pulled from the datasource).
Eval is a one-way binding that can be used with any namespace that will fulfill a proper evaluation. Dates, strings, method calls, etc. The namespace provided in your example just provides eval with a marker on where to get the data relevant.
The key here is the nature of the binding. Eval is a "fire and forget" sort of binding where as Bind is more rigid to facilitate the two-way.
The DataField property approach isn't complicated enough to support dot notation; it expects a direct reference in your underlying data source; it takes that field and checks the data source, which it can't find it by the exact string.
The second approach, eval, is more dynamic, but actually I wasn't sure if it supported dot notation... learn something everyday.
HTH.
It's necessary take a look to your DataSource, but you can do a simple test: convert the first column to a template column a try to Run.
In EntityFramework is possible Eval Properties using code like this: <%#Eval("Customer.Address.PostalCode") %>.
I dont know if it is your case, but if you provide more details about how to retrieve the DataSource we can help you.