Checked and Unchecked
For "overflow exceptions" generated when integer types participate in arithmetic operations and type conversion, some algorithms are not considered real "exceptions". On the contrary, this overflow is often used by programs. C# controls the needs of this particular situation by introducing checked and unchecked keywords. They can all be added before a statement block (such as: checked{...}), or before an arithmetic expression (such as: unchecked(x+y)). If a statement or expression with a checked flag is overflowed, an exception of type is thrown, and when a statement with an unchecked flag is overflowed, an exception is not thrown. Here is an example:
using System;
class Test{
static void Main() {
int num1=100000,num2=100000,
result=0;
checked{ try { result= num1 * num2;}
catch(２wException e){ (e); }
finally{ (result);}
}
unchecked{ try { result= num1 * num2;}
catch( (e){ (e);}
finally{ (result);}
}
}
}
Program output:
: Arithmetic operation resulted in an overflow.
at ()
0
1410065408
You can see the same arithmetic operation, using checked to throw an overflow exception, while unchecked just discards the overflowing bits and obtains the remaining 32-bit decimal integer value. It is worth pointing out that the code of the entire file can be specified with the "/checked" compiler option as checked semantics, and if not specified, it defaults to unchecked. If you specify the checked or unchecked flags in the program code at the same time and have the checked compiler option, except for the code with the flag unchecked, the rest have checked semantics.
For "overflow exceptions" generated when integer types participate in arithmetic operations and type conversion, some algorithms are not considered real "exceptions". On the contrary, this overflow is often used by programs. C# controls the needs of this particular situation by introducing checked and unchecked keywords. They can all be added before a statement block (such as: checked{...}), or before an arithmetic expression (such as: unchecked(x+y)). If a statement or expression with a checked flag is overflowed, an exception of type is thrown, and when a statement with an unchecked flag is overflowed, an exception is not thrown. Here is an example:
Copy the codeThe code is as follows:
using System;
class Test{
static void Main() {
int num1=100000,num2=100000,
result=0;
checked{ try { result= num1 * num2;}
catch(２wException e){ (e); }
finally{ (result);}
}
unchecked{ try { result= num1 * num2;}
catch( (e){ (e);}
finally{ (result);}
}
}
}
Program output:
Copy the codeThe code is as follows:
: Arithmetic operation resulted in an overflow.
at ()
0
1410065408
You can see the same arithmetic operation, using checked to throw an overflow exception, while unchecked just discards the overflowing bits and obtains the remaining 32-bit decimal integer value. It is worth pointing out that the code of the entire file can be specified with the "/checked" compiler option as checked semantics, and if not specified, it defaults to unchecked. If you specify the checked or unchecked flags in the program code at the same time and have the checked compiler option, except for the code with the flag unchecked, the rest have checked semantics.