What does Use of unassigned local variable mean

Question

I keep getting this error for annualRate  monthlyCharge  and lateFee   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  gt  100                                        monthlyCharge   balance    annualRate    1   12                                      else                                       monthlyCharge   0                                    return                            if  creditPlan     3                                 annualRate   0 15     15                  lateFee   0 00                   if  balance  gt  500                                        monthlyCharge    balance - 500     annualRate    1   12                                      else                                       monthlyCharge   0                                    return                            netBalance   balance -  lateFee   monthlyCharge                 Console WriteLine  Name   t t t  0    1    firstName  lastName               Console WriteLine  Account Number   t 0    accNumber               Console WriteLine  Credit Plane   t t 0   creditPlan               Console WriteLine  Account Late   t t 0    late               Console WriteLine  Balance   t t 0    balance               Console WriteLine  Late Fee   t t 0    lateFee               Console WriteLine  Interest Charge   t 0    monthlyCharge               Console WriteLine  Net Balance   t t 0   netBalance               Console WriteLine  Annual Rate   t t 0    annualRate               Console ReadKey

User · Answer

There are many paths through your code whereby your variables are not initialized, which is why the compiler complains.

Specifically, you are not validating the user input for creditPlan - if the user enters a value of anything else than "0","1","2" or "3", then none of the branches indicated will be executed (and creditPlan will not be defaulted to zero as per your user prompt).

As others have mentioned, the compiler error can be avoided by either a default initialization of all derived variables before the branches are checked, OR ensuring that at least one of the branches is executed (viz, mutual exclusivity of the branches, with a fall through else statement).

I would however like to point out other potential improvements:

Validate user input before you trust it for use in your code.
Model the parameters as a whole - there are several properties and calculations applicable to each plan.
Use more appropriate types for data. e.g. CreditPlan appears to have a finite domain and is better suited to an enumeration or Dictionary than a string. Financial data and percentages should always be modelled as decimal, not double to avoid rounding issues, and 'status' appears to be a boolean.
DRY up repetitive code. The calculation, monthlyCharge = balance * annualRate * (1/12)) is common to more than one branch. For maintenance reasons, do not duplicate this code.
Possibly more advanced, but note that Functions are now first class citizens of C#, so you can assign a function or lambda as a property, field or parameter!.

e.g. here is an alternative representation of your model:

    // Keep all Credit Plan parameters together in a model
    public class CreditPlan
    {
        public Func<decimal, decimal, decimal> MonthlyCharge { get; set; }
        public decimal AnnualRate { get; set; }
        public Func<bool, Decimal> LateFee { get; set; }
    }

    // DRY up repeated calculations
    static private decimal StandardMonthlyCharge(decimal balance, decimal annualRate)
    { 
       return balance * annualRate / 12;
    }

    public static Dictionary<int, CreditPlan> CreditPlans = new Dictionary<int, CreditPlan>
    {
        { 0, new CreditPlan
            {
                AnnualRate = .35M, 
                LateFee = _ => 0.0M, 
                MonthlyCharge = StandardMonthlyCharge
            }
        },
        { 1, new CreditPlan
            {
                AnnualRate = .30M, 
                LateFee = late => late ? 0 : 25.0M,
                MonthlyCharge = StandardMonthlyCharge
            }
        },
        { 2, new CreditPlan
            {
                AnnualRate = .20M, 
                LateFee = late => late ? 0 : 35.0M,
                MonthlyCharge = (balance, annualRate) => balance > 100 
                    ? balance * annualRate / 12
                    : 0
            }
        },
        { 3, new CreditPlan
            {
                AnnualRate = .15M, 
                LateFee = _ => 0.0M,
                MonthlyCharge = (balance, annualRate) => balance > 500 
                    ? (balance - 500) * annualRate / 12
                    : 0
            }
        }
    };

User · Answer

Give them a default value   double lateFee 0 0  double monthlyCharge   0 0  double annualRate   0 0    Basically  all possible paths don t initialize these variables

User · Answer

Use  quot default quot         string myString   default      double myDouble   defaul       if  String IsNullOrEmpty myString          myDouble   1 5       return myDouble

User · Answer

You don t assign values outside of the if statements     and it is possible that credit might be something other than 0  1  2  or 3  as  iomaxx noted   Try changing the separate if statements to a single if else if else if else   Or assign default values up at the top

User · Answer

If you declare the variable  annualRate  like  class Program      static double annualRate     public static void Main       Try it

User · Answer

Because if none of the if statements evaluate to true then the local variable will be unassigned   Throw an else statement in there and assign some values to those variables in case the if statements don t evaluate to true   Post back here if that doesn t make the error go away   Your other option is to initialize the variables to some default value when you declare them at the beginning of your code

User · Answer

Your assignments are all nested within your conditional if blocks which means that there is potential for them to never be assigned    At the top of your class  initialise them to 0 or some other value

User · Answer

The compiler is saying that annualRate will not have a value if the CreditPlan is not recognised   When creating the local variables   annualRate  monthlyCharge  and lateFee  assign a default value  0  to them   Also  you should display an error if the credit plan is unknown

User · Answer

Change your declarations to this   double lateFee   0 0  double monthlyCharge   0 0  double annualRate   0 0    The error is caused because there is at least one path through your code where these variables end up not getting set to anything

User · Answer

Not all code paths set a value for lateFee   You may want to set a default value for it at the top

User · Answer

The compiler isn t smart enough to know that at least one of your if blocks will be executed   Therefore  it doesn t see that variables like annualRate will be assigned no matter what   Here s how you can make the compiler understand   if  creditPlan     0                  else if  creditPlan     1                  else if  creditPlan     2                  else                  The compiler knows that with an if else block  one of the blocks is guaranteed to be executed  and therefore if you re assigning the variable in all of the blocks  it won t give the compiler error   By the way  you can also use a switch statement instead of ifs to maybe make your code cleaner

[c#] What does "Use of unassigned local variable" mean?

Examples related to c#

Examples related to unassigned-variable