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!!!!
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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