If statement – Does the assignment operator in c # take any other value than bool in any scenario?

I've recently started learning C # and I've learned that the if condition only takes the Boolean value from the assignment operator, as in the code below. But I wanted to know if there was a scenario where if takes a value other than bool.

I've tried to change the type of 'a'. in character but that gave me a compilation error.

Console.Write ("Enter a character:");
char c = (char) Console.Read ();
bool a;
if (a = Char.IsLetter (c))
{
if (a = Char.IsLower (c))
{
Console.WriteLine ("The character is lowercase.");
}
other
{
Console.WriteLine ("The character is uppercase.");
}
}
other
{
Console.WriteLine ("Not a character");
}