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

I recently started learning c# and got to know that the if condition takes only the boolean value for the assignment operator like in the below code. But I wanted to know if there is any scenario where if takes any value other than bool.

I tried changing the type of 'a' to char but it gave me a compile time 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.");
    }
    else
    {
        Console.WriteLine("The character is uppercase.");
    }
}
else
{
    Console.WriteLine("Not a character");
}