int.TryParse

int.TryParse method allows us to convert a string representation of a number to its 32-bit integer value.
TryParse(String, Int32)

TryParse method has two parameters, the first parameter is the string that you want to convert and the second parameter is modified with the out keyword. Also a return value indicates whether the TryParse is succeeded.
try { string num = "100"; int value; bool isSuccess = int.TryParse(num, out value); if(isSuccess) { value = value + 1; Console.WriteLine("Value is " + value); } } catch (FormatException e) { Console.WriteLine(e.Message); }Output : Value is 101
You can also use Int32.Parse() method to convert string to int
try { int strVal = Int32.Parse("2000"); strVal = strVal +1; Console.WriteLine("Value is " + strVal); } catch (FormatException e) { Console.WriteLine(e.Message); }Output : Value is 2001
Convert class

The C# language has a Convert class that allows you to convert a String to an Integer.
try { string no = "100"; int value = Convert.ToInt32(no); value = value + 1; Console.WriteLine("Value is " + value); } catch (FormatException e) { Console.WriteLine(e.Message); }Output : Value is 101
String to Number
Following are the Convert functions that convert string to different numerical types.
Converting String to decimal
decimal ToDecimal(String)
Converting String to float
float ToSingle(String)
Converting String to double
double ToDouble(String)
Converting String to short
short ToInt16(String)
Converting String to long
long ToInt64(String)
NEXT.....String and System.string