Errors

Even the most experienced developers make mistakes, and that is normal. In C#, errors can be of different types: compilation errors, runtime errors, and logical errors.

Compilation errors

These errors occur during program compilation and are related to syntax or type issues. For example, a type mismatch:


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int number = "123"; // Error: Cannot assign a string to a variable of type int
Line 1, Char 1

Runtime errors

These errors happen while the program is running, usually due to unexpected circumstances or incorrect data. For example, division by zero:


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int x = 10;
int y = 0;
int result = x / y; // Error: division by zero
Line 1, Char 1

Logical errors

These errors may not cause compilation or runtime errors, but they lead to incorrect results.


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int x = 5;
if (x > 0)
{
    Console.WriteLine("x is less than 0"); // Error, it should be: x is greater than 0
Line 1, Char 1

How to find and fix errors

Read compiler messages: they often explain in detail what went wrong.
Use the debugger: you can step through code and track variable values.
Logs: it is useful to add console output to track program execution.

Exercises

Run the code and look at the compiler error. What does it mean? Fix the code so that it runs without errors. Hint: you need to change int to string.


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int number = "123";
Console.WriteLine(number);
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Run the code and look at the runtime error. What does it mean? Fix the code so that it runs without errors.


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int x = 10;
int y = 0;
int result = x / y;
Console.WriteLine(result);
Line 1, Char 1

There is a logical error in the code. Fix it.


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int x = 5;
if (x > 0)
{
    Console.WriteLine("x is less than 0");
Line 1, Char 1