Unassigned variable in c#

Question

The variable in the last console.writeline is giving that has not been assigned being that it was in ifs, I wonder why.

string c, nome;
double s, sn;

Console.WriteLine("Escreva o nome:");
nome = Console.ReadLine();
Console.WriteLine("Escreva o salário:");
s = double.Parse(Console.ReadLine());
Console.WriteLine("Escreva a categoria:");
c = Console.ReadLine();

if (c == "a" || c == "c" || c == "f" || c == "h")
{
    sn = s * 1.10;
}
else if (c == "b" || c == "d" || c == "e" || c == "i" || c == "j" || c == "t")
{
    sn = s * 1.15;
}
else if (c == "k" || c == "r")
{
    sn = s * 1.25;
}
else if (c == "l" || c == "m" || c == "n" || c == "o" || c == "p" || c == "q" || c == "s")
{
    sn = s * 1.35;
}
else if (c == "u" || c == "v" || c == "x" || c == "y" || c == "w" || c == "z")
{
    sn = s * 1.50;
}
else
{
    Console.WriteLine("Categoria inválida!");
}

Console.WriteLine(" Nome: {0}\n Categoria: {1}\n Novo salário: R$ {2:0.00}", nome, c, sn);

Console.ReadKey();

Answer 1

Because if the code falls on else the variable will never receive a value.

Just initialize the variable with the default value.

double s, sn = 0;
// ...

Trying to read the code, it seems to me that it would be more reasonable to "cancel" the operation and return on else.

else
{
    Console.WriteLine("Categoria inválida!");
    return;
}

Answer 2

would like to know why

To answer your question, the reason this message occurs is that there is a path that the code can go through, which is the last else, where the variable sn will not have been assigned to any value and at the end of the program you are showing the value of that variable.

The solution @LINQ gave you to avoid the error is to start the variable with the value 0 at the beginning. Another way would be to put it in the last else an instruction sn = 0;