Foreach loop in C#

Arun Kurmi

hi friends,
I want to understand following code line by line.........
private void button1_Click(object sender, EventArgs e)
{
label2.Text = "";
label3.Text = "";

foreach (object checkeditem in checkedListBox1.Items)
//why we cannot use instead of above line : foreach(CheckedListBox checkeditem in checkedListBox1.Items)
{
string str = checkedListBox1.GetItemCheckState(checkedListBox1.Items.IndexOf(checkeditem)).ToString();
//meaning of this line
if (str == "Checked")
//why we used "Checked" .
{
label2.Text = label2.Text + checkeditem.ToString() + "\n";
}
else
{
label3.Text = label3.Text + checkeditem.ToString() + "\n";
}
}

thanks....

5 Replies

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Vulpes13y ago
Accepted answer
The foreach statement iterates over an enumerable object.

Broadly, an enumerable object is a collection which implements either IEnumerable or IEnumerable.

In the case of the latter, T will be the type of the iteration variable.

In the case of the former, the type of the iteration variable will usually be object.

However, suppose you have an ArrayList which actually contains nothing but strings even though internally they're stored in an object[]. If you specify the type of the iteration variable to be string, then this will work because the runtime will attempt to cast each object in the collection to string and will only raise an exception if the cast is invalid.

Now Enum.GetValues(typeof(KnownColor)) returns a System.Array object containing the values of the constants in the KnownColor enum. In other words it returns an array of KnownColor values even though these are stored internally in an object[].

The Array type implements IEnumerable and so, if you specify KnownColor to be the type of the iteration variable, the runtime successfully casts each object to KnownColor and the foreach statement works fine.
Arun Kurmi13y ago
thanks Vulpes, i understand but before this question i used foreach loop as...

1 foreach(Control ctl in Controls)

2 foreach(FontFamily f in FontFamily.Families)

so i think syntax of foreach as:

foreach(1 2 3 4)

1 classname
2 create object of class
3 in keyword
4 collection that return value for our created object
**************************************
but i see another ex. as
foreach(KnownColor val in Enum.GetValues(typeof(KnownColor)))

here KnownColor is not a class so
what is syntax for foreach???
Vulpes13y ago
Santosh, you're right!

http://www.c-sharpcorner.com/Members/?Type=legend
Santosh Yadav13y ago
Vulpes You are a legend.
Vulpes13y ago
The checkedListBox1.Items property returns a CheckedListBox.ObjectCollection (essentially a collection of objects), not a collection of CheckedListBoxes.

So the control variable in your foreach loop needs to be of type object, not CheckedListBox.

The checkedListBox1.GetItemCheckState() method returns a value of type CheckState which is an enum. The possible values are : Unchecked, Checked or Indeterminate.

This value is converted to a string (using ToString()) and the 'if' statement then tests whether the string value is "Checked" or not.