C# - Data Types

C# is a strongly-typed language. It means we must declare the type of a variable that indicates the kind of values it is going to store, such as integer, float, decimal, text, etc.

The following declares and initialized variables of different data types.

Example: Variables of Different Data Types
string stringVar = "Hello World!!";
int intVar = 100;
float floatVar = 10.2f;
char charVar = 'A';
bool boolVar = true;

C# mainly categorized data types in two types: Value types and Reference types. Value types include simple types (such as int, float, bool, and char), enum types, struct types, and Nullable value types. Reference types include class types, interface types, delegate types, and array types. Learn about value types and reference types in detail in the next chapter.

C# Data Types

Predefined Data Types in C#

C# includes some predefined value types and reference types. The following table lists predefined data types:

Type Description Range Suffix
byte 8-bit unsigned integer 0 to 255
sbyte 8-bit signed integer -128 to 127
short 16-bit signed integer -32,768 to 32,767
ushort 16-bit unsigned integer 0 to 65,535
int 32-bit signed integer -2,147,483,648
uint 32-bit unsigned integer 0 to 4,294,967,295 u
long 64-bit signed integer -9,223,372,036,854,775,808
ulong 64-bit unsigned integer 0 to 18,446,744,073,709,551,615 ul
float 32-bit Single-precision floating point type -3.402823e38 to 3.402823e38 f
double 64-bit double-precision floating point type -1.79769313486232e308 to 1.79769313486232e308 d
decimal 128-bit decimal type for financial and monetary calculations (+ or -)1.0 x 10e-28
7.9 x 10e28
char 16-bit single Unicode character Any valid character, e.g. a,*, \x0058 (hex), or\u0058 (Unicode)
bool 8-bit logical true/false value True or False
object Base type of all other types.
string A sequence of Unicode characters
DateTime Represents date and time 0:00:00am 1/1/01
11:59:59pm 12/31/9999

As you can see in the above table that each data type (except string and object) includes value range. The compiler will give an error if the value goes out of datatype's permitted range. For example, int data type's range is -2,147,483,648 to 2,147,483,647. So if you assign a value which is not in this range, then the compiler would give an error.

Example: Compile time error
// compile time error: Cannot implicitly convert type 'long' to 'int'.
int i = 21474836470; 

The value of unsigned integers, long, float, double, and decimal type must be suffix by u,l,f,d, and m, respectively.

Example: Value Suffix
uint ui = 100u;
float fl = 10.2f;
long l = 45755452222222l;
ulong ul = 45755452222222ul;
double d = 11452222.555d;
decimal mon = 1000.15m;

Alias vs .NET Type

The predefined data types are alias to their .NET type (CLR class) name. The following table lists alias for predefined data types and related .NET class name.

Alias .NET Type Type
byte System.Byte struct
sbyte System.SByte struct
int System.Int32 struct
uint System.UInt32 struct
short System.Int16 struct
ushort System.UInt16 struct
long System.Int64 struct
ulong System.UInt64 struct
float System.Single struct
double System.Double struct
char System.Char struct
bool System.Boolean struct
object System.Object Class
string System.String Class
decimal System.Decimal struct
DateTime System.DateTime struct

It means that whether you define a variable of int or Int32, both are the same.

int i = 345;
Int32 i = 345;// same as above 

Default Values

Every data type has a default value. Numeric type is 0, boolean has false, and char has '\0' as default value. Use the default(typename) to assign a default value of the data type or C# 7.1 onward, use default literal.

int i = default(int); // 0
float f = default(float);// 0
decimal d = default(decimal);// 0
bool b = default(bool);// false
char c = default(char);// '\0'

// C# 7.1 onwards
int i = default; // 0
float f = default;// 0
decimal d = default;// 0
bool b = default;// false
char c = default;// '\0'


The values of certain data types are automatically converted to different data types in C#. This is called an implicit conversion.

Example: Implicit Conversion
int i = 345;
float f = i;

Console.WriteLine(f); //output: 345

In the above example, the value of an integer variable i is assigned to the variable of float type f because this conversion operation is predefined in C#.

The following is an implicit data type conversion table.

Implicit Conversion From To
sbyte short, int, long, float, double, decimal
byte short, ushort, int, uint, long, ulong, float, double, decimal
short int, long, float, double, or decimal
ushort int, uint, long, ulong, float, double, or decimal
int long, float, double, or decimal.
uint long, ulong, float, double, or decimal
long float, double, or decimal
ulong float, double, or decimal
char ushort, int, uint, long, ulong, float, double, or decimal
float Double

Conversions from int, uint, long, or ulong to float and from long or ulong to double may cause a loss of precision. No data type implicitly converted to the char type.

However, not all data types are implicitly converted to other data types. For example, int type cannot be converted to uint implicitly. It must be specified explicitly, as shown below.

Example: Explicit Conversion
public static void Main()
    int i = 100;
    uint u = (uint) i;

In the above example, integer i is converted to uint explicitly by specifying uint in the brackets (uint). This will convert an integer to uint.