foreach (DataRow dr in dt.Rows)

Well foreach fetched one by one object among the collection and For loop fetched based on index of object.

Like if you want to apply for loop for the same scenario then

For(int i=0;i<dt.rows.count;i++)
{
DataRow row = dt.rows[i];
}

Where i Plays an important role that on object at which index should be fetched. and while in foreach it grabs one by one object from the collection.

Article provided by thatraja is good but it lacks understanding may THIS[^] will help you in better way to understand it.

Hi,
A for loop is run on a condition, and will run until the
condition is false. Usually this is a counter, and the
condition is a threshold.

Ex for(int i=0;i<dt.Rows.count;i++)
{
}
Here counter is run until it is not setisfied i<dt.Rows.count.
So here you can take any number for condition.

A foreach runs through an array
executing the code in the the loop once for each element of
the array, with the array element.

Ex .
foreach (DataRow dr in dt.Rows)
{
}

Here dr checks each element of the dt.rows

It checks the each element of the rows of Datatable.

FOREACH Vs. FOR (C#)[^]

Difference between For and Foreach loop[^]