How to check which textBox is empty ,checkBox is not checked

Give each input control a unique x:Name in the XAML, e.g:

<TextBox x:Name="t1"/>
<CheckBox x:name="c1" />

You could then reference each control by its name:

if(t1.Text == "some text...")
{
//do this
}
else
{
//do that...
}

if(c1.IsChecked == true)
{
//checkbox is checked...do this
}
else
{
//do that...
}

if(string.IsNullOrEmpty(t1.Text))
{
//t1 is empty...
}

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