Solved

how to query datatable using linq?

Posted on 2011-03-12
6
755 Views
Last Modified: 2013-12-17
hi,

I have datatable, and I wanna query specific customer record from datatable using his id by linq,

so how can I do that using linq?

while I was trying, I got null value selected as return !, here is my code snippet:

 
private Customer GetCustomerInfo(string id)
        {
            Customer cm = null;
            var customers = (from customer in dtCustomers.AsEnumerable()
                         //where customer.Field<string>("id") == id
                         select new { 
                             CustomerId = customer["id"],
                             CustomerEnName = customer["EnName"],
                             CustomerArName = customer["ArName"],
                             CustomerClass = customer["EnClass"],
                             CustomerCellPhone = customer["CellPhone"],
                             Telephone = customer["Telephone"],
                             CustomerEmail = customer["Email"],
                             CustomerIsActive = customer["Active"],
                             CustomerNationalId = customer["NationalId"],
                             CustomerNationalIdType = customer["NationalIdType"]
                         }).Take(1);

            foreach (var c in customers)//I got customers always null even the id is correct
            {
                cm = new Customer(c.CustomerId.ToString(), "LMR-" + Other.changeTo6Digits(c.CustomerId.ToString()), c.CustomerEnName.ToString(), c.CustomerArName.ToString(), "", c.CustomerCellPhone.ToString(), c.Telephone.ToString(), c.CustomerEmail.ToString(), c.CustomerClass.ToString(), c.CustomerIsActive.ToString(), "", c.CustomerNationalId.ToString(), c.CustomerNationalIdType.ToString());
                break;
            }
            return cm;

        }

Open in new window

private Customer GetCustomerInfo(string id)
        {
            Customer cm = null;
            var customers = (from customer in dtCustomers.AsEnumerable()
                         //where customer.Field<string>("id") == id
                         select new { 
                             CustomerId = customer["id"],
                             CustomerEnName = customer["EnName"],
                             CustomerArName = customer["ArName"],
                             CustomerClass = customer["EnClass"],
                             CustomerCellPhone = customer["CellPhone"],
                             Telephone = customer["Telephone"],
                             CustomerEmail = customer["Email"],
                             CustomerIsActive = customer["Active"],
                             CustomerNationalId = customer["NationalId"],
                             CustomerNationalIdType = customer["NationalIdType"]
                         }).Take(1);

            foreach (var c in customers)//I got customers always null even the id is correct
            {
                cm = new Customer(c.CustomerId.ToString(), "LMR-" + Other.changeTo6Digits(c.CustomerId.ToString()), c.CustomerEnName.ToString(), c.CustomerArName.ToString(), "", c.CustomerCellPhone.ToString(), c.Telephone.ToString(), c.CustomerEmail.ToString(), c.CustomerClass.ToString(), c.CustomerIsActive.ToString(), "", c.CustomerNationalId.ToString(), c.CustomerNationalIdType.ToString());
                break;
            }
            return cm;

        }

Open in new window

0
Comment
Question by:njgroup
  • 3
  • 2
6 Comments
 
LVL 18

Expert Comment

by:Gary Davis
ID: 35115920
Seems like you want to have the DataTable Rows collection as enumerable, not the DataTable itself.

Gary Davis
0
 
LVL 63

Accepted Solution

by:
Fernando Soto earned 500 total points
ID: 35116191
Hi njgroup;

A couple of things your query returns a Anonymous type and NOT a Customer. We know this because in your select clause you have this, select new {, which does not name the type to create and so an Anonymous type is created. Note in the code snippet I have changed that to this, new DtCustomer {, which states to create the new objects of type DtCustomer, the class I also added to the code snippet. An Anonymous type really has no use outside of the method that created it therfore the reason for creating a concrete type DtCustomer to return to the caller. I also changed the Take(1) to FirstOrDefault(). The Take() method returns, "If count is less than or equal to zero, source is not enumerated and an empty IEnumerable(Of T) is returned.", where the FirstOrDefault returns a null if no result was found, better for error checking.

private DtCustomer GetCustomerInfo(string id)
{
    var customer  = (from customer in dtCustomers.AsEnumerable()
                     where customer.Field<string>("id") == id
                     select new DtCustomer { 
                         CustomerId = customer.Field<int>("id"),
                         CustomerEnName = customer.Field<string>("EnName"),
                         CustomerArName = customer.Field<string>("ArName"),
                         CustomerClass = customer.Field<string>("EnClass"),
                         CustomerCellPhone = customer.Field<string>("CellPhone"),
                         Telephone = customer.Field<string>("Telephone"),
                         CustomerEmail = customer.Field<string>("Email"),
                         CustomerIsActive = customer.Field<string>("Active"),
                         CustomerNationalId = customer.Field<int>("NationalId"),
                         CustomerNationalIdType = customer.Field<string>("NationalIdType")
                     }).FirstOrDefault();

    return customer;
}

public class DtCustomer
{
    public int CustomerId {get; set;}    
    public string CustomerEnName {get; set;}    
    public string CustomerArName {get; set;}    
    public string CustomerClass {get; set;}    
    public string CustomerCellPhone {get; set;}    
    public string Telephone {get; set;}
    public string CustomerEmail {get; set;}
    public string CustomerIsActive {get; set;}
    public int CustomerNationalId {get; set;}
    public string CustomerNationalIdType {get; set;} 
}

Open in new window


Fernando
0
 

Author Comment

by:njgroup
ID: 35119903
thanks very much, but I get an strange error on where statement

Unable to cast object of type 'System.Int32' to type 'System.String'.


even I have it as sting but I dont know really why it give variable as integer!



 
private Customer GetCustomerInfo(string id)
        {
            var customer1 = (from customer in dtCustomers.AsEnumerable()
                            where customer.Field<string>("id") == id // <-- exception generated here
                            select new Customer
                            {
                                id = customer.Field<string>("id"),
                                enName = customer.Field<string>("EnName"),
                                arName = customer.Field<string>("ArName"),
                                type = customer.Field<string>("EnClass"),
                                cellPhone = customer.Field<string>("CellPhone"),
                                tel = customer.Field<string>("Telephone"),
                                email = customer.Field<string>("Email"),
                                isActive = customer.Field<string>("Active"),
                                nationalId = customer.Field<string>("NationalId"),
                                nationalIdType = customer.Field<string>("NationalIdType")
                            }).FirstOrDefault();

            return customer1;
        }

Open in new window

0
Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

 

Author Comment

by:njgroup
ID: 35119934
Ok, I solve the problem :D thanks very much
0
 

Author Closing Comment

by:njgroup
ID: 35119936
solution is perfect
0
 
LVL 63

Expert Comment

by:Fernando Soto
ID: 35121463
Not a problem, glad I was able to help.  ;=)
0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Parsing a CSV file is a task that we are confronted with regularly, and although there are a vast number of means to do this, as a newbie, the field can be confusing and the tools can seem complex. A simple solution to parsing a customized CSV fi…
The ECB site provides FX rates for major currencies since its inception in 1999 in the form of an XML feed. The files have the following format (reducted for brevity) (CODE) There are three files available HERE (http://www.ecb.europa.eu/stats/exch…
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question