Multi tool use

Possible way to do to with foreach instead of for [closed]

I am trying to convert DataGridView columns into an ArrayList. I would like to make this code into a foreach version. I tried to follow this answer but, it doesn't worked for me. With this for method my problem is, when I am deleting a bunch of rows from the datagridview, then it gives an error or my binary search doesn't work well. That's why I want to try with foreach method.

DataGridView

ArrayList

foreach

for

foreach

for (int i = 0 ; i < dataGridView2.Rows.Count; i++)

ListOfPeople[i] = dataGridView2.Rows[i].Cells[0].Value.ToString().Trim();



This question appears to be off-topic. The users who voted to close gave this specific reason:

foreach

DataGridView Row row

foreach

dataGridView2.Rows

ArrayList.sort();

ArrayList.ToArray();

4 Answers
4

As an alternative to loops you can try query dataGridView2.Rows with a help of Linq and build ListOfPeople in one go:

dataGridView2.Rows

ListOfPeople

// ArrayList is an obsolete class; let's use List<string>
List<string> ListOfPeople = dataGridView2
.Rows
.OfType<DataGridViewRow>()
.Select(row => row.Cells[0].Value.ToString().Trim())
.ToList();


Why can't you use foreach likewise for any other collection

foreach

foreach (DataGridViewRow row in dataGridView2.Rows)
// code here



The problem with the conversion of for to foreach is what to do with loop index i. Two situations are possible - when you need i, and when you don't need i.

for

foreach

i

i

i

When i is necessary, use Select that passes the index to you, like this:

i

Select

foreach (var p in dataGridView2.Rows.Select((r, i) => new Row = (DataGridViewRow)r, Index = i)
ListOfPeople[p.Index] = p.Row.Cells[0].Value.ToString().Trim();



When i is not necessary, you can use "straight" foreach, or even drop the loop altogether:

i

foreach

ListOfPeople = dataGridView2.Rows.Cast<DataGridViewRow>()
.Select(r => r.Cells[0].Value.ToString().Trim())
.ToList();


The old-school answer to your question (how to use a foreach instead of for) is pretty close to what @Rahul describes. However, the Rows collection was a pre-generic collection (i.e., it's been there since .NET v1.x), and when you foreach over it, you get objects, and not rows. Instead, this works:

foreach

for

foreach (var row in dataGridView2.Rows.Cast<DataGridViewRow>())
// code here



The old school way of keeping track of an index variable (i) is something like:

i

var i = 0;
foreach (var row in dataGridView2.Rows.Cast<DataGridViewRow>())

// your code here
++i;