1. Data Types
Imran Rashid
CTO at ManiWeber Technologies

2. Outline
What are Types?
Classes & Structures

3. What are Types?

4. What are Types?
In C# when we store data, we have to say what type of data we are storing
A type defines what information a variable contains
Variables in C# are strongly typed
A typed implies minimum, maximum values
Once declared, a variable’s type can’t be changed
C# Built-in Data Types
Logical
Numeric
Characters & Strings
Classes & Structures
Objects

5. Classes & Structures

6. object o1 = new Object(); object o2 = o1; // o2 references o1
Classes & Structures
Types are represented in .NET as classes or structures
Both have members: fields & methods
You can create instances of either a class or structure
Classes vs. Structures
Structures are value types
Classes are reference types
int v1 = 5;
int v2 = v1; // v2 is copy of v1
object o1 = new Object();
object o2 = o1; // o2 references o1

7. Classes & Structures Common Structures
Numeric and logical built-in types are structures
Examples
bool
a true/false value
int
a 32-bit integer
double
a 32-bit floating point value
decimal
a 128-bit high-precision value

8. System.Boolean System.Char Classes & Structures
Logical & Character Types
All .NET types are members of System
You should only use type alias (fully qualified names)
C# Type
.NET Type
Min
Max
bool
Boolean
false
true
char
Char
U+0000
U+ffff
System.Boolean
System.Char

9. Classes & Structures Integer Types C# Type .NET Type Min Max byte Byte
255
sbyte
SByte
-128
127
short
Int16
-32,768
32,767
ushort
UInt16
int
Int32
-2, 147, 483, 648
2, 147, 483, 647
unint
UInt32
4, 294, 967, 295
long
Long
-9.22 x 1018
9.22 x 1018
ulong
Ulong
1.84 x 1019

10. Classes & Structures Floating-Point and Decimal Types
Decimal is a 128-bit, high-precision type
Appropriate for currency and other financial values
C# Type
.NET Type
Min
Max
Precision
float
Single
±1.5e-45
±3.4e38
7 digits
double
Double
±5.0e-324
±1.7e308
15-16 digits
decimal
Decimal
-7.9 x 1028
7.9 x 1028
28-29 digits

11. C# Type .NET Type Max string String 2, 147, 483, 647*
Classes & Structures
Strings
Decimal is a 128-bit, high-precision type
*Theoretical! Memory is more important!
Mobile app where memory is small
System.String is a class, not a structure
C# has give a lot of tools to help with string immutability
C# Type
.NET Type
Max
string
String
2, 147, 483, 647*

12. Any ?