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Convert.ToInt32 Method (String, Int32)

Converts the String representation of a number in a specified base to an equivalent 32-bit signed integer.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

public static int ToInt32 (
	string value,
	int fromBase
public static int ToInt32 (
	String value, 
	int fromBase
public static function ToInt32 (
	value : String, 
	fromBase : int
) : int
Not applicable.



A String containing a number.


The base of the number in value, which must be 2, 8, 10, or 16.

Return Value

A 32-bit signed integer equivalent to the number in value. -or- Zero if value is a null reference (Nothing in Visual Basic).

Exception typeCondition


fromBase is not 2, 8, 10, or 16.


value, which represents a non-base 10 signed number, is prefixed with a negative sign.


value contains a character that is not a valid digit in the base specified by fromBase. The exception message indicates that there are no digits to convert if the first character in value is invalid; otherwise, the message indicates that value contains invalid trailing characters.




The return value is less than Int32.MinValue or larger than Int32.MaxValue.

If fromBase is 16, you can prefix the number specified by the value parameter with "0x" or "0X".

Because the negative sign is not supported for non-base 10 numeric representations, the ToInt32(String,Int32) method assumes that negative numbers use two’s complement representation. In other words, the method always interprets the highest-order binary bit of an integer (bit 31) as its sign bit. As a result, it is possible to write code in which a non-base 10 number that is out of the range of the Int32 data type is converted to an Int32 value without the method throwing an exception. The following example increments Int32.MaxValue by one, converts the resulting number to its hexadecimal string representation, and then calls the ToInt32(String,Int32) method. Rather than throwing an exception, the method displays the message, “0x80000000 converts to 2147483648.”

When performing binary operations or numeric conversions, it is always the responsibility of the developer to verify that a method uses the appropriate numeric representation to interpret a particular value. As the following example illustrates, you can ensure that the method handles overflows appropriately by first retrieving the sign of the numeric value before converting it to its hexadecimal string representation. Then throw an exception if the conversion back to an integer yields a negative value when the original value was positive.



.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0

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