Check if list is empty in C#

Question

I have a generic list object. I need to check if the list is empty.

How do I check if a List<T> is empty in C#?

So what's wrong with using if (list.Count == 0) { /* ... */ }? — Bart van Nierop
– Bart van Nierop, Commented Sep 18, 2013 at 8:27

Tim Schmelter · Accepted Answer · 2021-08-26 07:02:29Z

223

You can use Enumerable.Any:

bool isEmpty = !list.Any();
if(isEmpty)
{
    // ...
}

If the list could be null you could use:

bool isNullOrEmpty = list?.Any() != true;

edited Aug 26, 2021 at 7:02

answered Sep 18, 2013 at 8:22

Tim Schmelter

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4 Comments

ᴍᴀᴛᴛ ʙᴀᴋᴇʀ Over a year ago

Would it not be best to check whether list == null first?

daviesdoesit Over a year ago

@ᴍᴀᴛᴛʙᴀᴋᴇʀ, var someList = new List<string>(); would be instantiated( and therefore not be null) but would be empty of elements to process

ruffin Mar 6 at 14:13

I disagree w/ Microsoft, but apparently the new coolness is to avoid .Any(): To determine whether a collection type has any elements, it's more efficient and clearer to use the Length, Count, or IsEmpty (if possible) properties than to call the Enumerable.Any method. Any(), which is an extension method, uses language integrated query (LINQ). It's more efficient to rely on the collection's own properties, and it also clarifies intent. suggesting you use strings.Length > 0; & not strings.Any();

Tim Schmelter Mar 6 at 15:36

@ruffin: especially the "clearer" is doubtful: "To determine whether a collection type has any elements, it's clearer to use the Length, Count...". So dont use Any if you want to determine if something has any elements, because it's unclear, better check if the total count or length is greater than 0. Funny

Grant Thomas · Accepted Answer · 2013-09-18 08:22:22Z

107

If the list implementation you're using is IEnumerable<T> and Linq is an option, you can use Any:

if (!list.Any()) {

}

Otherwise you generally have a Length or Count property on arrays and collection types respectively.

answered Sep 18, 2013 at 8:22

Grant Thomas

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3 Comments

Adrian Lopez Over a year ago

As quick note: list.Any has much better performance than count.

noox Over a year ago

@AdrianLopez: can you elaborate on that? If you have a .Count or .Length property as with List what could .Any() possibly do to be faster than checking the property of the collection which keeps track of the the current length or count? If you only have an Enumerator, then .Any() is of course faster than .Count() > 0. See also: stackoverflow.com/questions/305092/… or stackoverflow.com/questions/5741617/…

NetMage Over a year ago

@noox Looking at the (.Net Core) source, it seems Any checks to validate that retrieving the count is cheap before testing it, in cases where you have an IListProvider<> that doesn't track the count, it will enumerate once instead.

Kuzgun · Accepted Answer · 2013-09-18 08:24:23Z

45

    If (list.Count==0){
      //you can show your error messages here
    } else {
      //here comes your datagridview databind 
    }

You can make your datagrid visible false and make it visible on the else section.

answered Sep 18, 2013 at 8:24

Kuzgun

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2 Comments

Spencer Wieczorek Over a year ago

@NetMage That's not how it works for list. It's an O(1) operation and there is no iterations done for counting elements. See List<T>.Count.

NetMage Over a year ago

@SpencerWieczorek You are correct, that comment was old as well as wrong :) Though in general, I would still prefer Any() as expressing intent better, as well as being more performant when you don't know you have an actual List<T>.

Jeroen van Langen · Accepted Answer · 2020-07-04 14:13:35Z

27

What about using the Count property.

 if(listOfObjects.Count != 0)
 {
     ShowGrid();
     HideError();
 }
 else
 {
     HideGrid();
     ShowError();
 }

edited Jul 4, 2020 at 14:13

user12026681

answered Sep 18, 2013 at 8:22

Jeroen van Langen

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5 Comments

Moslem Ben Dhaou Over a year ago

Count is a property not a method

Grant Thomas Over a year ago

@MoslemBenDhaou Depends on whether it's the Linq extension method exposed/being called, or native to the object.

Moslem Ben Dhaou Over a year ago

@GrantThomas I took it as a List<T> object but yes you are correct.

Sabri Mevis Over a year ago

what if listOfObjects is null?

Jeroen van Langen Over a year ago

@SabriMeviş a collection/ienumerable/list returned from a method should never be null. It should be an empty collection instead.

Moslem Ben Dhaou · Accepted Answer · 2016-01-21 08:26:16Z

11

You should use a simple IF statement

List<String> data = GetData();

if (data.Count == 0)
    throw new Exception("Data Empty!");

PopulateGrid();
ShowGrid();

edited Jan 21, 2016 at 8:26

answered Sep 18, 2013 at 8:24

Moslem Ben Dhaou

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4 Comments

Jabba Over a year ago

Simplest and best way IMO.

daviesdoesit Over a year ago

If the method returns a null, the Count property will fail. To keep the code concise, consider the null reference check operator "?". Example "if (data?.Count == 0) . . . . ." or the classic null check "if (data != null && someOtherCondition) ....."

daviesdoesit Over a year ago

Paste the following code into a dotnetfiddle and you'll see the System.NullReferenceException: Object reference not set to an instance of an object.

using System; using System.Collections.Generic; 					 public class Program { 	public static void Main() 	{ 		List<string> stringList = null; 		if (stringList.Count == 0) 		{ 			Console.WriteLine("no items in collection"); 		} 	} }

Moslem Ben Dhaou Over a year ago

@daviesdoesit that would be beyond the scope of the question. This snippet clearly assumes data is defined.

TalentTuner · Accepted Answer · 2013-09-18 08:25:10Z

8

var dataSource = lst!=null && lst.Any() ? lst : null;
// bind dataSource to gird source

answered Sep 18, 2013 at 8:25

TalentTuner

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Comments

Baahubali · Accepted Answer · 2013-09-18 08:22:41Z

4

gridview itself has a method that checks if the datasource you are binding it to is empty, it lets you display something else.

answered Sep 18, 2013 at 8:22

Baahubali

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Comments

muskatnuss · Accepted Answer · 2024-10-15 16:40:03Z

3

Some of the answers above recommend using list.Any() and some of them recommend using list.Count > 0.

When using .Any() on a List, Visual Studio shows the following warning: CA1860: Prefer comparing 'Count' to 0 rather than using 'Any()', both for clarity and for performance

If you check the respective rule code CA1860 Microsoft recommends to "Avoid using 'Enumerable.Any()' extension method".

Therefore using list.Count > 0 is recommended over using list.Any()

edited Oct 15, 2024 at 16:40

answered Aug 17, 2024 at 16:20

muskatnuss

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7 Comments

Luuk Over a year ago

Could not reproduce this CA1860 error. Please add some code which allows me to reproduce this. (see: dotnetfiddle.net/pMQlLW )

muskatnuss Over a year ago

@Luuk Even if you can't reproduce CA1860, you can still take a look at the resource I provided. I edited my answer to contain the version of Visual Studio I am using.

muskatnuss Over a year ago

@Luuk If I copy the code you provided in your dotnetfiddle to my Visual Studio, I see the warning I mentioned in my answer.

Andrew Morton Over a year ago

@Luuk You should see three dots under list in the code you showed in VS2022. If you hover the cursor over list.Any you'll see a box pop up with the CA1860 message at the bottom.

Luuk Over a year ago

@AndrewMorton: Sorry, I am too new to C# to be bothered by those three dots, so I ignored them (until now!).

|

David MacCrimmon · Accepted Answer · 2013-09-18 08:24:03Z

1

If you're using a gridview then use the empty data template: http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.emptydatatemplate.aspx

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSqlDataSource" 
        autogeneratecolumns="true"
        runat="server">

        <emptydatarowstyle backcolor="LightBlue"
          forecolor="Red"/>

        <emptydatatemplate>

          <asp:image id="NoDataImage"
            imageurl="~/images/Image.jpg"
            alternatetext="No Image" 
            runat="server"/>

            No Data Found.  

        </emptydatatemplate> 

      </asp:gridview>

answered Sep 18, 2013 at 8:24

David MacCrimmon

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2 Comments

Grant Thomas Over a year ago

This is very ASP.NET specific.

David MacCrimmon Over a year ago

I'm not a winforms guys but isn't a gridview asp.net specific. It's a datagridview in forms?

safinilnur · Accepted Answer · 2024-01-23 20:40:24Z

-1

Sometimes you need to force rerender parent component when you don't have a direct access to this parent component. Then you can use:

this.$parent.$forceUpdate();

answered Jan 23, 2024 at 20:40

safinilnur

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