CODEWITHSUNDEEP
c#list
Surya Matadewa
Surya Matadewa

Reputation: 1027

Replace value in list

hi i have collection list named ~runs~ 

 class CRun {
   int slideQuestion;
   int studentId;
   string answer;
 }

 public static List<CRun> runs = new List<CRun>();

this is how i add data to collection list

myRun.slideQuestion = 1;
myRun.studentId = 15;
myRun.answer = 2;

0 = { 1, 15, 2}
1 = { 1, 12, 5}
2 = { 2, 15, 3}
3 = { 2, 12, 4}

then i have data like this { 1, 15, 1}
i wanna replace list[0] (same slideQuestion & studentID) so it's become

**0 = {1, 15, 1}**
1 = { 1, 12, 5}
2 = { 2, 15, 3}
3 = { 2, 12, 4}

i wanna make condition like this 

if ~slideQuestion~ AND ~studentID~ already in list 
    //replace answer in some location
else (add data)
    runs.add(myRun);

how to do it?

Upvotes: 0

Views: 116

Answers (3)

Mihai Hantea
Mihai Hantea

Reputation: 1743

Using linq: 

var r = runs.FirstOrDefault(c => c.slideQuestion == 10 && c.studentId == 15);
if (r != null)
{
    r.answer = "something";
}
else
{
    runs.Add(new CRun
    {
       slideQuestion = 10,
       studentId = 15,
       answer = "something"
     });   
 }

Change your class to this:

class CRun {
   public int slideQuestion { get; set; }
   public  int studentId { get; set; }
   public  string answer { get; set; }
}

You cannot access the class fields if they are private. Change them to auto-properties.

Upvotes: 1

Suresh Kumar Veluswamy
Suresh Kumar Veluswamy

Reputation: 4363

Assuming this is the new slidequestion, student id, and the answer you want to replace are in these variables

int slideQuestion = 1;
int studentId = 15;
string newAnswer = "1";

Here is how you search for run and update with the new answer if it exists or create a new run

var runInList = (from run in runs where run.SlideQuestion == slideQuestion && studentId == studentId select run).FirstOrDefault();

if (runInList != null)
{
    runInList.Answer = newAnswer;
}
else
{
    runs.Add(new CRun { SlideQuestion = slideQuestion, StudentId = studentId, Answer = newAnswer });
}

Upvotes: 1

Mark Seemann
Mark Seemann

Reputation: 233487

Here's how to replace the first element in the list:

runs[0] = newValue;

Upvotes: 1

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