The following table shows the keywords for built-in C# types, which are aliases of predefined types in the System namespaces.

| C# Type| .NET Framework Type|
| ------ | ------ |
| bool | System.Boolean|  
| byte| System.Byte|  
| sbyte | System.SByte|  
| char | System.Char|
| decimal| System.Decimal|  
| double | System.Double|  
| float| System.Single|  
| int | System.Int32| 
| uint| System.UInt32|  
| long | System.Int64|  
| ulong | System.UInt64|  
| object| System.Object|  
| short | System.Int16|  
| ushort| System.UInt16|  
| string | System.String|

The C# type keywords and their aliases are interchangeable. For example, you can declare an integer variable by using either of the following declarations:

int number = 123;
System.Int32 number = 123;