If richtextbox is empty to display a msgbox

[tambovskya]

if i press for example button1, and i want it to have a statement,


button1.

if richtextbox 1 = "" then,
msgbox1. "you have no text".

how do you do this in c#?

I USE VISUAL C# 2010 EXPRESS!

[tambovskya]

also one more question, how would i code that, example,

if richtextbox 1 contains word "like",
then change that word to "whatever"

[tambovskya]

Also is it possible to do this?

for example,

if richtextbox1 contains word "because", then
change it to any of these words,

example,
example,
example,

and random selector.

[Deranged]

I use this for a textbox, pretty sure it's close to the same as a rich text box.

if (String.IsNullOrEmpty(textbox.Text))
                MessageBox.Show("No text detected, please enter something!");
else
{
     //Whatever you want it to do after it's no longer empty.
}