如何在C＃中计算列表上相同值的数量

Question

Here's the code:

List<string> Listahan = new List<string>();
Listahan.Add("TEST1");
Listahan.Add("TEST2");
Listahan.Add("TEST3");
Listahan.Add("TEST4");
Listahan.Add("TEST5");
Listahan.Add("TEST5");
Listahan.Add("TEST1");

Then what I want is when I enter TEST1 on my textbox it will output it's count which is 2. Thank in advance.

Answer 1

string textboxVal = "TEST1";    
int testOccurence = Listahan.Count(str => str == textboxVal);

If you are using .NET 2.0 and don't use LINQBridge :

int testOccurence = Listahan.FindAll(delegate (string str) { return str == textboxVal;})
                            .Count;

some notes: it might be the case, that you may also need case insensitive search. For example user can enter "test1" and receive meaningful results. You can use next code to achieve this:

Listahan.Count(str => string.Equals(str, textboxVal, StringComparison.OrdinalIgnoreCase))

Answer 2

You also can use GroupBy to count all the text first if you often access:

var dic = Listahan.GroupBy(x => x)
                  .ToDictionary(g => g.Key, g => g.Count());

int count = dic["TEST1"]; //count of 'TEST1'