as (C# Reference)
Used to perform conversions between compatible reference types. For example:
string s = someObject as string;
if (s != null)
{
// someObject is a string.
}
Remarks
The as operator is like a cast except that it yields null on conversion failure instead of raising an exception. More formally, an expression of the form,
expression as type
is equivalent to,
expression is type ? (type)expression : (type)null
except that expression is evaluated only once.
Note that the as operator only performs reference conversions and boxing conversions. The as operator cannot perform other conversions, such as user-defined conversions, which should instead be performed using cast expressions.
Example
// cs_keyword_as.cs
// The as operator.
using System;
class Class1
{
}
class Class2
{
}
class MainClass
{
static void Main()
{
object[] objArray = new object[6];
objArray[0] = new Class1();
objArray[1] = new Class2();
objArray[2] = "hello";
objArray[3] = 123;
objArray[4] = 123.4;
objArray[5] = null;
for (int i = 0; i < objArray.Length; ++i)
{
string s = objArray[i] as string;
Console.Write("{0}:", i);
if (s != null)
{
Console.WriteLine("'" + s + "'");
}
else
{
Console.WriteLine("not a string");
}
}
}
}
Output
0:not a string 1:not a string 2:'hello' 3:not a string 4:not a string 5:not a string
C# Language Specification
For more information, see the following sections in the C# Language Specification:
6 Conversions
7.9.10 The as operator
See Also
Reference
C# Keywords
is (C# Reference)
?: Operator (C# Reference)
Operator Keywords (C# Reference)