Convert.ToInt32() vs int.TryParse() : Which One Should You Use?

Convert.ToInt32() vs int.TryParse(): Which One Should You Use?

When converting a string to an integer in C#, Convert.ToInt32() and int.TryParse() are commonly used. While they appear to give the same result, they differ significantly in terms of behavior and performance characteristics.

Convert.ToInt32(string)

int number = Convert.ToInt32("123");
  • Converts a string to an integer.
  • Throws a FormatException if conversion fails.
try
{
    int number = Convert.ToInt32("abc");
    Console.WriteLine($"Conversion succeeded: {number}");
}
catch (FormatException)
{
    // FormatException occurs
    Console.WriteLine("Conversion failed: Invalid format");
}

Exceptions are costly in terms of performance, especially if they occur frequently. While try-catch blocks themselves have minimal impact during normal execution, throwing exceptions creates additional overhead such as allocating exception objects and collecting stack traces. Therefore, in scenarios with frequent invalid input, this method can be inefficient.

int.TryParse(string, out int)

int.TryParse("123", out int number);
  • Returns a boolean indicating success or failure.
  • Does not throw an exception even if parsing fails.
  • If it fails, the output variable is set to 0.
  • The converted value is stored in the out variable number.
  • From C# 7.0, you can declare out variables directly in the method call.
bool success = int.TryParse("abc", out int number);
if (success)
{
    Console.WriteLine($"Conversion succeeded: {number}");
}
else
{
    Console.WriteLine("Conversion failed"); // number == 0
}

Because it doesn't throw exceptions, this method is better suited for uncertain user input or cases where failure is expected and should be handled gracefully.

Other TryParse Variants

In addition to int.TryParse(), many primitive types offer similar methods that safely convert a string input to the desired type. 

float.TryParse("3.14", out float f);   // string → float
bool.TryParse("true", out bool b);     // string → bool
long.TryParse("10000000000", out long l); // string → long

These variants also return false on failure without throwing exceptions, and set the out variable to its default value.

One Thing to Keep in Mind...

int.TryParse() returns false if the conversion fails, but it does not tell you why it failed.

For example, all of the following different failure cases:

// Contains letters – invalid format
int.TryParse("apple", out int a);

// Contains a decimal point – cannot convert to int
int.TryParse("3.14", out int b);

// Number too large – exceeds int range
int.TryParse("999999999999999", out int c);

In all three cases, the result is simply false, and the output variable is set to 0. That means TryParse only tells you that the conversion failed — it does not provide any reason.

While TryParse() is fast and avoids exceptions, if you need to understand why it failed, you'll need to implement additional logic to inspect the input more precisely.

Summary

  • If you're sure the string is a valid number, Convert.ToInt32() is simple to use — but exceptions can impact performance.
  • If there's a chance of invalid input, int.TryParse() is safer and more efficient.
  • Use exceptions only for truly exceptional cases; avoid using them for flow control.

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