Diffrence Int32.parse, Convert.ToInt32, Int32.TryParse

-------------------Int32.parse(string)-------------------

Int32.Parse (string s) method converts the string representation of a number to its 32-bit signed integer equivalent.
When s is null reference, it will throw ArgumentNullException.
If s is other than integer value, it will throw FormatException.
When s represents a number less than MinValue or greater than MaxValue, it will throw OverflowException.

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Example
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string s1 = "1234";
string s2 = "1234.65";
string s3 = null;
string s4 = "123456789123456789123456789123456789123456789";

int result;
bool success;

result = Int32.Parse(s1); //-- 1234
result = Int32.Parse(s2); //-- FormatException
result = Int32.Parse(s3); //-- ArgumentNullException
result = Int32.Parse(s4); //-- OverflowException


-------------------Convert.ToInt32(string)-------------------

Convert.ToInt32(string s) method converts the specified the string representation of 32-bit signed integer equivalent. This calls in turn Int32.Parse () method.
When s is null reference, it will return 0 rather than throw ArgumentNullException
If s is other than integer value, it will throw FormatException.
When s represents a number less than MinValue or greater than MaxValue, it will throw OverflowException

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Example
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result = Convert.ToInt32(s1); //-- 1234
result = Convert.ToInt32(s2); //-- FormatException
result = Convert.ToInt32(s3); //-- 0
result = Convert.ToInt32(s4); //-- OverflowException



-------------------Int32.TryParse(string, out int)------------------

Int32.Parse(string, out int) method converts the specified the string representation of 32-bit signed integer equivalent to out variable, and returns true if it parsed successfully, false otherwise. This method is available in C# 2.0
When s is null reference, it will return 0 rather than throw ArgumentNullException.
If s is other than integer value, the out variable will have 0 rather than FormatException.
When s represents a number less than MinValue or greater than MaxValue, the out variable will have 0 rather than OverflowException.

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Example
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success = Int32.TryParse(s1, out result);
//-- success => true; result => 1234
success = Int32.TryParse(s2, out result);
//-- success => false; result => 0
success = Int32.TryParse(s3, out result);
//-- success => false; result => 0
success = Int32.TryParse(s4, out result);
//-- success => false; result => 0

Convert.ToInt32 is better than Int32.Parse, since it return 0 rather than exception. But, again according to the requirement this can be used. TryParse will be best since it handles exception itself always.