How to avoid null values in LINQ command?

Question

I am trying to search the object from its list using entity framework.

I have following structure of the object

public class Product
{
    public int Id { get; set; }
    public string ProductName { get; set; }
    public double Size { get; set; }
}

and I create the list of the product

private List<Product> AddProducts()
{
    List<Product> ProductList = new List<Product>();

    oProduct Product = new Product();
    oProduct.Id = 1;
    oInventory.ProductName = "Product1";
    oProduct.Size = 25;
    ProductList.Add(oProduct);

    oProduct Product = new Product();
    oProduct.Id = 2;
    oInventory.ProductName = "Product2";
    oProduct.Size = 25;
    ProductList.Add(oProduct);

    return ProductList;           
}

Now, I am trying to search the object form the above list form ProductName parameter.

I have used below code.

public ActionResult Index(string productname = "", string size = "")
{
    var oProdList = from ProdList in AddProducts() select oProdList;
    oProdList = oProdList.Where(oProd => oProd.ProductName.ToUpper().Contains(ProductName.ToUpper().Trim())|| oProd.Size.ToString().ToUpper().Contains(size.ToUpper().Trim()));
    ViewBag.ProductList = oProdList;
    return View();
}

Now Please check picture below, I have list of products and I am trying to find the Product1 by typing it in text box and I keep the size textbox blank. now when I click on submit , I pass these two varibles for searching in Index method (above one) but the LINQ command returns the both records, Product1 and Product 2 but it should return only one record

How to deal with this ?

enter image description here

Jason Roell · Accepted Answer · 2014-03-08 15:30:52Z

This worked for me and is how a search algorithm should work. You want to && the parameters if they are both provided but || them if one of the arguments is missing.

Also its good to note that an input of "2" will match "25" for the size because we are preforming a Contains. If you want it only to match when you enter "25" and not "2" set it to == instead of Contains. Same goes for productname.

public class Product
{
  public int Id { get; set; }
  public string ProductName { get; set; }
  public double Size { get; set; }
}

private List<Product> AddProducts()
{
  List<Product> ProductList = new List<Product>();

  var p = new Product();
  p.Id = 1;
  p.ProductName = "Product1";
  p.Size = 25;
  ProductList.Add(p);


  var p2 = new Product();
  p2.Id = 2;
  p2.ProductName = "Product2";
  p2.Size = 25;
  ProductList.Add(p2);

  return ProductList;           
}

public ActionResult Index(string productname = "", string size = "")
{
  var oProdList = from p in AddProducts() select p;

  if (!string.IsNullOrWhiteSpace(productname) && !string.IsNullOrWhiteSpace(size))
  {
     oProdList = oProdList.Where(p => p.ProductName.ToUpper().Trim().Contains(productname.ToUpper().Trim()) && p.Size.ToString().Contains(size.Trim()));
  }
  else
  {
    oProdList = oProdList.Where(p => !string.IsNullOrWhiteSpace(productname) ? p.ProductName.ToUpper().Trim().Contains(productname.ToUpper().Trim()) : p.ProductName.ToUpper().Trim() == productname.ToUpper().Trim() || !string.IsNullOrWhiteSpace(size) ? p.Size.ToString().Contains(size.Trim()) : p.Size.ToString() == size.Trim());
  }

  ViewBag.ProductList = oProdList;
  return View();
}

Hossein Salmanian · Accepted Answer · 2014-03-08 07:23:05Z

1

that happen because every string value contain string empty and your parameter size default value set to string.empty so you should check it for filtering the result like this

    oProdList = oProdList.Where(
        oProd =>(productname == string.Empty ? false:
                oProd.ProductName.ToUpper().Contains(productname.ToUpper().Trim()))
                || (size == string.Empty ? false:oProd.Size.ToString().
                ToUpper().Contains(size.ToUpper().Trim()))
        );

edited Mar 8, 2014 at 7:23

answered Mar 8, 2014 at 6:33

Hossein Salmanian

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1 Comment

bnil Over a year ago

Its working only for the ProductName, If I mention the ProductName and Size both, still it return on the basis of Product Name only...It do not consider the Size.

Tinu · Accepted Answer · 2014-03-08 05:27:03Z

0

I think the cause might be because of you are converting size to string

Try this

public ActionResult Index(string productname = "", string size = "0")
        {
            var oProdList = from ProdList in AddProducts() select oProdList;


      oProdList = oProdList.Where(oProd => oProd.SectionName.ToUpper().Contains(ProductName.ToUpper().Trim())|| oProd.Size == (double)size));


            ViewBag.ProductList = oProdList;
            return View();

        }

answered Mar 8, 2014 at 5:27

Tinu

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2 Comments

bnil Over a year ago

I think problem is with blank values.... if I set size parameter blank then it return both the records...

Tinu Over a year ago

you should be comparing the same types, i suggest you make Size as nullable ( double? ) so that you can check for blank sizes

Victor Mukherjee · Accepted Answer · 2014-03-08 06:29:20Z

0

You can use the null coalescing operator here.

    oProdList = oProdList.Where(oProd => (!String.IsNullOrEmpty((ProductName??"").Trim()) &&
    oProd.ProductName.ToUpper().Contains(ProductName.ToUpper().Trim()) 
|| (!String.IsNullOrEmpty((size??"").Trim()) && oProd.Size.ToString().ToUpper().Contains(size.ToUpper().Trim())));

edited Mar 8, 2014 at 6:29

answered Mar 8, 2014 at 6:22

Victor Mukherjee

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1 Comment

bnil Over a year ago

I am using it for searching, User can enter only productName or may be both ProductName and Size.... Both time it should work...so I am using OR not AND

Ganesh · Accepted Answer · 2014-03-08 06:32:18Z

0

You need to specify to ignore search if the search params are empty.

Try this:

var productList = from ProdList in AddProducts()
where (productname.Trim() == string.Empty || ProdList.ProductName.ToUpper().Contains(ProductName.ToUpper().Trim()))
&& (size.Trim() == string.Empty || ProdList.Size.ToString().ToUpper().Contains(size.ToUpper().Trim()))
select ProdList;

edited Mar 8, 2014 at 6:32

answered Mar 8, 2014 at 6:04

Ganesh

2451 silver badge9 bronze badges

3 Comments

Ganesh Over a year ago

Try the edited version. I added the Trim() to the params. The values might not be empty when you are posting them.

bnil Over a year ago

Problem is with blank values...It returns true in command so its return call values...

bnil Over a year ago

only works when I put Productname only, Not working when I put the values in both textbox... User can put both field or any of field...We cant assume user can put productName everytime...

Damith · Accepted Answer · 2014-03-08 05:28:49Z

-1

if(!String.IsNullOrWhiteSpace(oProd.SectionName)){
    oProdList = oProdList.Where(oProd => oProd.SectionName.ToUpper().Contains(ProductName.ToUpper().Trim());
}

if(!String.IsNullOrWhiteSpace(oProd.Size)){
    oProdList = oProdList.Where(oProd => oProd.Size.ToUpper().Contains(size.ToUpper().Trim());
}

answered Mar 8, 2014 at 5:28

Damith

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4 Comments

bnil Over a year ago

It will overwrite the oProdList, if both command return different result set ?

bnil Over a year ago

I dont want to overwrite it... I want to do a search with the more than one parameter, if any parameter is blank then it returns all the records...

bnil Over a year ago

I am trying to figure out since two days, Why its so difficult ?

Damith Over a year ago

why down vote!!! here what i'm doing is building query, it will not fetch the data until you call call something like ToList() etc..

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