Capturing iteration variables - CSharp Custom Type

CSharp examples for Custom Type:Lambda

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Introduction

When you capture the iteration variable of a for loop, C# treats that variable as though it was declared outside the loop.

The same variable is captured in each iteration. 


Action[] actions = new Action[3];

for (int i = 0; i < 3; i++)
   actions [i] = () => Console.Write (i);

foreach (Action a in actions) 
   a();     // 333

We can illustrate this better by expanding the for loop as follows: 

Action[] actions = new Action[3];
int i = 0;
actions[0] = () => Console.Write (i);
i = 1;
actions[1] = () => Console.Write (i);
i = 2;
actions[2] = () => Console.Write (i);
i = 3;
foreach (Action a in actions) a();    // 333

To write 012, assign the iteration variable to a local variable that's scoped inside the loop: 

Action[] actions = new Action[3];
for (int i = 0; i < 3; i++)
{
 int loopScopedi = i;
 actions [i] = () => Console.Write (loopScopedi);
}
foreach (Action a in actions) a();     // 012

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