How Can I Clear All Data In One Click

First of all you are using && (AND) operator instead of || (OR) in your IF statement.
Second, you are casting one control to three types of Control in one loop pass.

Assuming that you want to clear only Text property of controls you have few solutions:

1. You need to check your control for every possible type you want to clear like this:

foreach (Control cntl in this.Controls)
{
    if (cntl is TextBox)
    {
        ((TextBox)cntl).Text = string.Empty;
    }
    else if (cntl is ComboBox)
    {
        ((ComboBox)cntl).Text = string.Empty;
    }
    else if (cntl is RichTextBox)
    {
        ((RichTextBox)cntl).Text = string.Empty;
    }
}

2. Or, you can set Text property directly, beceause Control type has it, so any type that inherits from the Control will has it too. This will do the job:

foreach (Control ctrl in this.Controls)
{
    ctrl.Text = string.Empty;
}

My advice is to put controls that you will be clearing on any container control, like Panel or GroupBox.

Hope it helps.

If may sound a bit off-topic, but if I had to deal with a project where I need to clean up different controls in one loop I would add an extension method to all of the involved type (using the same name). That extension method will clean the control.
Now in my loop I would invoke that extension method using reflection...

if (cntl is TextBox) {
TextBox txt = (TextBox)cntl;
txt.Text = "";}

if (cntl is ComboBox ) {
ComboBox cmb = (ComboBox )cntl;
cmb.Items.Clear();
}

private void clear()
{
foreach (Control cntl in this.Controls)
{
if (cntl is TextBox || cntl is ComboBox || cntl is RichTextBox)
{

((TextBox)cntl).Text = string.Empty;
((ComboBox)cntl).Text = string.Empty;
((RichTextBox)cntl).Text = string.Empty;
}
}
}
private void button1_Click(object sender, EventArgs e)
{
clear();
}
try this

Don't use any condition, simply using type casting, you can reset all the controls.
See my cod below,

foreach (Control cntl in this.Controls)
{
    ((TextBox)cntl).Text = string.Empty;
    ((ComboBox)cntl).SelectedIndex= 0;
    ((RichTextBox)cntl).Text = string.Empty;
}

-KR