The use of unassigned local variable in c# error: What should you do?

Question

I get the error: use of unassigned local variable in C# when I try to run the program below:

using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
 namespace Lab_5___Danny_Curro
 {
  class Program
  {
  static void Main(string[] args)
  {
  string firstName;
  string lastName;
  int accNumber;
  string creditPlan;
  double balance;
  string status;
  Boolean late = false;
  double lateFee;
  double monthlyCharge;
  double annualRate;
  double netBalance;
 
 
  Console.Write("Enter First Name: ");
  firstName = Console.ReadLine();
 
  Console.Write("Enter Last Name: ");
  lastName = Console.ReadLine();
 
  Console.Write("Enter Account Number: ");
  accNumber = Convert.ToInt32(Console.ReadLine());
 
 
  Console.Write("Enter Credit Card Plan Number[Blank Will Enter Plan 0]: ");
  creditPlan = Console.ReadLine();
 
  Console.Write("Enter Balance: ");
  balance = Convert.ToDouble(Console.ReadLine());
 
  Console.Write("Is This Account Late?: ");
  status = Console.ReadLine().Trim().ToLower();
 
  if (creditPlan == "0")
  {
  annualRate = 0.35; //35%
  lateFee = 0.0;
  monthlyCharge = balance * (annualRate * (1 / 12));
  return;
  }
 
  if (creditPlan == "1")
  {
  annualRate = 0.30; //30%
  if (status == "y")
  {
  late = true;
  }
 
  else if (status == "n")
  {
  late = false;
  }
  if (late == true)
  {
  lateFee = 25.00;
  }
  monthlyCharge = balance * (annualRate * (1 / 12));
  return;
  }
  if (creditPlan == "2")
  {
  annualRate = 0.20; //20%
  if (status == "y")
  {
  late = true;
  }
 
  else if (status == "n")
  {
  late = false;
  }
  if (late == true)
  {
  lateFee = 35.00;
  }
  if (balance > 100)
  {
  monthlyCharge = balance * (annualRate * (1 / 12));
  }
  else
  {
  monthlyCharge = 0;
  }
  return;
  }
  if (creditPlan == "3")
  {
  annualRate = 0.15; //15%
  lateFee = 0.00;
 
  if (balance > 500)
  {
  monthlyCharge = (balance - 500) * (annualRate * (1 / 12));
  }
  else
  {
  monthlyCharge = 0;
  }
  return;
  }
  netBalance = balance - (lateFee + monthlyCharge);
 
 
  Console.WriteLine("Name: 			 {0} {1}", firstName, lastName);
  Console.WriteLine("Account Number: 	{0}", accNumber);
  Console.WriteLine("Credit Plane: 		{0}",creditPlan);
  Console.WriteLine("Account Late: 		{0}", late);
  Console.WriteLine("Balance: 		{0}", balance);
  Console.WriteLine("Late Fee: 		{0}", lateFee);
  Console.WriteLine("Interest Charge: 	{0}", monthlyCharge);
  Console.WriteLine("Net Balance: 		{0}",netBalance);
  Console.WriteLine("Annual Rate: 		{0}", annualRate);
  Console.ReadKey();
  }
  }
 }

The error appears the system notifies as follows:

Use of unassigned local variable

I tried to solve it with another sample. I got the reference in the community forum, but it still returned an invalid result. If someone knows the solution, please give me the support. Thanks!

lyytutoria · Accepted Answer

The cause: At most only one of your if block can be executed, but the the compiler is not intelligent enough to notice this. And that compiler also doesn’t know the variables such as annualRate will always be assigned. Therefore, the error appears in your system. Solution: If you want this error disappears, you have to make the compiler understand easily. Below are some ways I recommend you:

if (creditPlan == "0")
{
 // ...
}
else if (creditPlan == "1")
{
 // ...
}
else if (creditPlan == "2")
{
 // ...
}
else
{
 // ...
}

The compiler is aware of an if/else blocks guarantees a block to be executed. Therefore, if the variable is assigned in all blocks, the compiler will not give this error. If you want to make your code more readable, you could also use switch statements instead of ifs.

Hugo Chevallier · Answer

This is how to change your declarations

double lateFee = 0.0;
double monthlyCharge = 0.0;
double annualRate = 0.0;

This error occurs because at least one of your code paths contains variables that are not set to anything.

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The use of unassigned local variable in c# error: What should you do?