Using the Get* Methods to Read Column Values

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
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Using the Get* Methods to Read Column ValuesUsing the Get* Methods to Read Column ValuesBefore I show you the other Get* methods that read column values, you need to know thestandard C# types and the values they support. You need to know these so that you canunderstand the type compatibilities between C# and SQL Server shown later. Table 9.3shows the standard C# types, along with the underlying .NET type and the values that canbe stored in the C# type. Table 9.3: STANDARD C# AND .NET TYPESC# .NET VALUESTYPE TYPEbool Boolean A Boolean true or false value.byte Byte An 8-bit unsigned integer between 0 and 28 - 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 *1028 with 28 significant figures of precision.double Double A 64-bit floating-point number between approximately +/-5 *10- 324 and approximately +/-1.7 *10308 with 15 to 16 significant figures of precision.float Single A 32-bit floating-point number between approximately +/-1.5 *10- 45 to approximately +/-3.4 *1038 with 7 significant figures of precision.Guid Guid A 128-bit unsigned integer value (16 bytes) that that is unique across all computers and networks.int Int32 A 32-bit signed integer between -231 (-2,147,483,648) and 231 - 1 (2,147,483,647).long Int64 A 64-bit signed integer between -263 (- 9,223,372,036,854,775,808) and 263 - 1 (9,223,372,036,854,775,807).sbyte SByte An 8-bit signed integer between -27 (-128) and 27 - 1 (127).short Int16 A 16-bit signed integer between -215 (-32,768) and 215 - 1 (32,767).string String A variable-length string of 16-bit Unicode characters. Table 9.3: STANDARD C# AND .NET TYPESC# .NET VALUESTYPE TYPEuint UInt32 A 32-bit unsigned integer between 0 and 232 - 1 (4,294,967,295).ulong UInt64 A 64-bit unsigned integer between 0 and 264 - 1 (18,446,744,073,709,551,615).ushort UInt16 A 16-bit unsigned integer between 0 and 216 - 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 theDataReader Get* methods that return each C# type. You use this table to figure out whichmethod to call to get a specific column type. For example, if you need to get the value ofa bigint column, you call the GetInt64() method that returns a long. Table 9.4: SQL SERVER TYPES, COMPATIBLE STANDARD C# TYPES, AND GET* METHODSSQL SERVER TYPE COMPATIBLE STANDARD C# TYPE GET* METHODbinary byte[] GetBytes()bigint long GetInt64()bit bool GetBoolean()char string GetString()datetime DateTime GetDateTime()decimal decimal GetDecimal()float double GetDouble()image byte[] GetBytes()int int GetInt32()money decimal GetDecimal()nchar string GetString()ntext string GetString()nvarchar string GetString()numeric decimal GetDecimal()real float GetFloat()smalldatetime DateTime GetDateTime()smallint short GetInt16()smallmoney decimal GetDecimal() Table 9.4: SQL SERVER TYPES, COMPATIBLE STANDARD C# TYPES, AND GET* METHODSSQL SERVER TYPE COMPATIBLE STANDARD C# TYPE GET* METHODsql_varient object GetValue()text string GetString()timestamp byte[] GetBytes()tinyint byte GetByte()varbinary byte[] GetBytes()varchar string GetString()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 youll see how to use some of the methods shown in Table 9.4.