Question

I never did Console programming so got stuck in this silly thing:

Console.Write("Enter customer's salary: ");
string sal = Console.Write("{0}! ", Console.ReadLine().ToString());

It generates error: Cannot implicitly convert type ‘void’ to ‘string’

Answer 1

Console.Write is a void method, it does not return what it writes to the console.
What you actually need is string.Format:

string sal = string.Format("{0}! ", Console.ReadLine());

Also, the extra ToString() at the end is redundant (as noted in the comments) for two reasons:

1. Console.ReadLine already returns a string
2. String formatting functions accept objects as parameters, they automatically convert to string if needed.