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Question

How do I filter a generic list in .Net2.0?

Answer 1

+5 A:

As you're using .Net2.0 you can't use LINQ, however you can use a delegate and the FindAll method:

string criteria = EmployeeName.Text.Trim().ToLower();
List<EmployeeInfo> resultList = empInfoList.FindAll(
   delegate(EmployeeInfo p)
   {
      return p.EmployeeName.ToLower().Contains(criteria);
   }
);

GenericTypeTea 2010-07-05 12:44:54

what pros and cons comparing with foreach loop?

Arseny 2010-07-05 12:49:12

@Arseny - read this here: http://stackoverflow.com/questions/674632/generic-list-findall-vs-foreach

GenericTypeTea 2010-07-05 12:50:05

Seems like perfect to me but I am getting Null record in resultlist. When I have placed break point there I found that it's not going to the inner braket of delegate. But my empInfoList have 24 records.Please suggest.

Rahul 2010-07-05 13:05:19

I don't think breaks inside the delegate get hit unless you step into the delegate from a line break on the same line as FindAll. I don't understand why you're getting null records as FindAll only returns records that match... Can you post up some code of what you've tried?

GenericTypeTea 2010-07-05 13:07:31

List<EmployeeInfo> empInfoList = objCustomer.GetEmployees(user.PasswordQuestion, ref errorMsg);List<EmployeeInfo> resultList = empInfoList.FindAll( delegate(EmployeeInfo p) { return p.Name == txtSearchEmployee.Text.Trim(); } ); grvEmployees.DataSource = resultList; grvEmployees.DataBind();

Rahul 2010-07-05 13:53:11

Please let me know if any other information is required.

Rahul 2010-07-05 13:53:36

Put in a breakpoint before you set the DataSource and see if any of the items in resultList are null before you set the DataSource.

GenericTypeTea 2010-07-05 13:55:33

I have checked the same, empInfoList is giving me 24 revcords. I have put "Cal" in the textbox, which is also coming correct. but when breakpoint comes to the delegate(EmployeeInfo p) part, it's going directly to Gridview bind statement, and resultList is returning Null records.

Rahul 2010-07-05 13:59:43

Try the code I added and let me know if it still does the same thing or if it works without the FindAll method.

GenericTypeTea 2010-07-05 14:04:46

You're not disposing the empInfoList are you?

GenericTypeTea 2010-07-05 14:06:42

This seems to be working fine, but it is working when user has entered the excat name, I have made it as a search box, I want to use something like "like" operator.

Rahul 2010-07-05 14:12:31

Ahh... When you say it's returning Null records, do you mean that the COUNT of the resultList is 0?

GenericTypeTea 2010-07-05 14:13:45

If you remember, today only you answered me the question in which I questioned about filling the dataset with list view, that is working absolutely fine but I can't assign dataset to gridview because their parameters are not same. That's why I thought to do the same with the list.

Rahul 2010-07-05 14:14:35

yes , count is 0

Rahul 2010-07-05 14:15:21

Rahul - you confused me there. I've fixed the answer, let me know if it's any better. Don't use the word null in place of 0. They're not the same thing. That's why I didn't understand what the problem was.

GenericTypeTea 2010-07-05 14:16:52

Actually, Gridview has predefined template, and Dataset conatins more column which is leading in error. but this list EmployeeInfo is returning me a correct column name with correct formating. That's the reason I want to go ahead with the list.

Rahul 2010-07-05 14:23:44

Try my updated code.

GenericTypeTea 2010-07-05 14:26:27

Absolute perfect.. Thanks a lot for your time and effort.. :) Thanks again :) :)

Rahul 2010-07-05 14:30:30

No worries. Any time.

GenericTypeTea 2010-07-05 14:31:26

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How do I filter a generic list in .Net2.0?

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