Getting ArgumentOutOfRangeException using for loop in Blazor component

Question

I\'m trying out Blazor and I\'m getting this exception when I\'m trying to load a list of checkboxes using a for loop.

I\'ve created the list here:

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Answer 1

You can solve it like this:

@for (int j = 0; j < Months.Count; j++)
{
    int i = j;  // a local copy to solve the capture problem

    

        
@Months[i].MonthName
        

    
}

Which means this is a new, Blazor specific variation on 'capturing the loop variable'.

When you look at the .razor.g.cs file you can see that the checkbox requires two lambda's, here is a snippet:

 __value => Months[i].isMonthChecked = __value

and after the for-loop, when the RenderTree is being built, the value of i will be Count for all months.

Using Count()-1 in the original code (your temporary fix) will prevent the exception but note that the form will not function properly, the wrong month will be checked.

General conclusion: don't mix EditForm with a for-loop. foreach() is safe.