Using the Get* Methods to Read Column Values
Before I show you the other Get* methods that read column values, you need to know the
standard C# types and the values they support. You need to know these so that you can
understand the type compatibilities between C# and SQL Server shown later. Table 9.3

shows the standard C# types, along with the underlying .NET type and the values that can
be stored in the C# type.
Table 9.3: STANDARD C# AND .NET TYPES
C#
TYPE
.NET
TYPE
VALUES
bool Boolean A Boolean true or false value.
byte Byte An 8-bit unsigned integer between 0 and 2
8
- 1(255).
char Char A 16-bit Unicode character.
DateTime DateTime A date and time between 12:00:00 AM January 1, 0001 and
11:59:59 PM December 31, 9999.
decimal Decimal A fixed precision and scale number between approximately +/-1.0
*10
-28
and approximately +/-7.9 *10
28
with 28 significant figures
of precision.
double Double A 64-bit floating-point number between approximately +/-5 *10
-
324

- 1 (127).
short Int16 A 16-bit signed integer between -2
15
(-32,768) and 2
15
- 1
(32,767).
string String A variable-length string of 16-bit Unicode characters.
Table 9.3: STANDARD C# AND .NET TYPES
C#
TYPE
.NET
TYPE
VALUES
uint UInt32 A 32-bit unsigned integer between 0 and 2
32
- 1 (4,294,967,295).
ulong UInt64 A 64-bit unsigned integer between 0 and 2
64
- 1
(18,446,744,073,709,551,615).
ushort UInt16 A 16-bit unsigned integer between 0 and 2
16
- 1 (65,535).
Note The standard C# types are defined in the System namespace.
Table 9.4
shows the SQL Server types, the compatible standard C# types, and the
DataReader Get* methods that return each C# type. You use this table to figure out which
method to call to get a specific column type. For example, if you need to get the value of
a bigint column, you call the GetInt64() method that returns a long.

uniqueidentifier Guid GetGuid()
Note You can see the SQL Server types and the values supported by those types in Table
2.3 of Chapter 2, "Introduction to Databases."

Note The Get* methods are defined in all of the DataReader classes and work for all
databases.
Next you'll see how to use some of the methods shown in Table 9.4
.