How to handle null values in C#. When I am entering characters in a char array i want to leave some values blank or empty (null). But when i do that my program terminates giving me an error. The error is shown in the pic below. What should i do to handle this exception. Please help!!!!
Jump to PostShowing your code would be more helpful than just the output.
Showing your code would be more helpful than just the output.
What should i do to handle this exception.
Don't cause it in the first place. If values can be null, be sure to check for null when doing things like output and use a safe alternative.
This is the full code:
class Program
{
static void Main(string[] args)
{
char[] array = new char[20];
//char[] array1 = new char[20];
Console.WriteLine("Enter your answers Choice: A,B,C,D");
driverexam d = new driverexam();
d.input(array);
d.passed(array);
d.totalcorrect(array);
d.totalincorrect(array);
d.questionmissed(array);
}
}
class driverexam
{
char[] answer = { 'B', 'D', 'A', 'A', 'C', 'A', 'B', 'A', 'C', 'D', 'B', 'C', 'D', 'A', 'D', 'C', 'C', 'B', 'D', 'A' };
int i,count=0,wrong=0,missed=0;
public void input(char[] array)
{
if (array != null)
{
for (i = 0; i < array.Length; i++)
{
array[i] = Convert.ToChar(Console.ReadLine());
}
}
}
public void passed(char[] array)
{
for (i = 0; i < array.Length; i++)
{
if (array[i] == answer[i])
{
count++;
}
}
if (count >= 15)
{
Console.WriteLine("YOU HAVE PASSED!!!!!!!!");
}
else
Console.WriteLine("YOU HAVE FAILED!!!!!!!!");
}
public void totalcorrect(char[] array)
{
count = 0;
for (i = 0; i < array.Length; i++)
{
if (array[i] == answer[i])
{
count++;
}
}
Console.WriteLine("Total Correct : {0}", count);
}
public void totalincorrect(char[] array)
{
for (i = 0; i < array.Length; i++)
{
if (array[i] != answer[i])
{
wrong++;
}
}
Console.WriteLine("Total InCorrect : {0}", wrong);
}
public void questionmissed(char[] array)
{
missed = 0;
for (i = 0; i < array.Length; i++)
{
if (char.IsWhiteSpace(array[i]))
{
missed++;
}
}
Console.WriteLine("Total Questions : {0}", missed);
}
}
}
It works fine if I dont leave any value as blank but when i leave a value empty or blank then my program terminates and i get the error stated as above. How should i handle such exceptions cause i want to calculate the no of questions missed?
On line 30, if you just tap return for a test with no answer you will get a null value from ReadLine, wich you are trying to convert to a char wich gives your error.
So test for null values( as deceptikon proposes) before you do the conversion to a char.
Maybe the simplest way is to use a dummy char ( a space, an 'X' etc.) for a test not answered.
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