c# - How to get sum of the values from List?

Question

I want to get sum of the values from list.

For example: I have 4 values in list 1 2 3 4 I want to sum these values and display it in Label

Code:

protected void btnCalculate_Click(object sender, EventArgs e)
{
    string monday;
    TextBox txtMonTot;
    List<string> monTotal = new List<string>();

    if (Application["mondayValues"] != null)
    {
        List<string> monValues = Application["mondayValues"] as List<string>;
        for (int i = 0; i <= gridActivity.Rows.Count - 1; i++)
        {
            GridViewRow row = gridActivity.Rows[i];
            txtMonTot = (TextBox)row.FindControl("txtMon");
            monday = monValues[i];
            monTotal.Add(monday);
        }
    }
}

Since this comment is being upvoted, it should be mentioned that as others have commented, you need a reference to System.Linq to use list.Sum(). — OldDog, Dec 12 '16 at 05:44
Possible duplicate of [C# List of objects, how do I get the sum of a property](https://stackoverflow.com/questions/4351876/c-sharp-list-of-objects-how-do-i-get-the-sum-of-a-property) — Brian Hooper, Aug 30 '17 at 09:21

score 98 · Accepted Answer · edited Sep 16 '13 at 09:40

98

You can use the Sum function, but you'll have to convert the strings to integers, like so:

int total = monValues.Sum(x => Convert.ToInt32(x));

edited Sep 16 '13 at 09:40

Sriram Sakthivel

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answered Sep 16 '13 at 09:38

Roy Dictus

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2

If they have to be summed, why are the lists of string in the first place? – Abhitalks Sep 16 '13 at 09:40
3

You probably don't need the lambda `Sum(Convert.ToInt32)` – Sayse Sep 16 '13 at 09:42
6

To clarify, @Sayse is not wrong, and the syntax is valid. The problem is Sum has two overloads, one which accepts a func that returns a decimal and one that accepts a func that returns a Nullable. With the method group syntax, it can't tell which overload Convert.ToDecimal matches. The lambda syntax works around the problem wrapping Convert.ToDecimal in another method which always returns a decimal. – Tim Copenhaver Sep 17 '13 at 13:41
1

Make sure to add `using System.Linq;`. – Justin Helps Oct 09 '20 at 16:03
Just to clarify if you are going to use the `List().Sum()` method you have to add `using System.Linq;` to the top of your code – Gharbad The Weak Sep 02 '22 at 17:47

score 18 · Answer 2 · answered Sep 16 '13 at 09:40

18

Use Sum()

 List<string> foo = new List<string>();
 foo.Add("1");
 foo.Add("2");
 foo.Add("3");
 foo.Add("4");

 Console.Write(foo.Sum(x => Convert.ToInt32(x)));

Prints:

10

answered Sep 16 '13 at 09:40

DGibbs

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I was just about to ask the same – NDJ Sep 16 '13 at 09:44
1

I really don´t see why this answer should get downvoted! Maybe he read this Question http://meta.stackexchange.com/questions/17204/six-simple-tips-to-get-stack-overflow-reputation-fast and applied rule no. 2 – makim Sep 16 '13 at 09:45

score 10 · Answer 3 · answered Sep 16 '13 at 09:38

10

You can use LINQ for this

var list = new List<int>();
var sum = list.Sum();

and for a List of strings like Roy Dictus said you have to convert

list.Sum(str => Convert.ToInt32(str));

answered Sep 16 '13 at 09:38

makim

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Prasad Kanaparthi · Answer 4 · 2013-09-16T11:12:37.943

2

How about this?

List<string> monValues = Application["mondayValues"] as List<string>;
int sum = monValues.ConvertAll(Convert.ToInt32).Sum();

edited Sep 16 '13 at 11:12

answered Sep 16 '13 at 09:44

Prasad Kanaparthi

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c# - How to get sum of the values from List?

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