The SqlDataReader Class

Table 9.2: SqlDataReader METHODS METHOD RETURN TYPE DESCRIPTION GetBoolean bool Returns the value of the specified column as a bool.. The long value returned is the number of byte val

You use an object of the SqlDataReader class to read rows retrieved from a SQL Server database, an object of the OleDbDataReader class to read rows from any database that supports OLE DB, such as Oracle or Access, and an object of the OdbcDataReader class

to read rows from any data-base that supports ODBC Table 9.1 shows some of the

SqlDataReader properties

Table 9.1: SqlDataReader PROPERTIES

PROPERTY TYPE DESCRIPTION

Depth int Gets a value indicating the depth of nesting for the current row FieldCount int Gets the number of columns in the current row

IsClosed bool Gets a bool value indicating whether the data reader is closed RecordsAffected int Gets the number of rows added, modified, or removed by

execution of the SQL statement

Note Although the SqlDataReader class is specific to SQL Server, many of the properties and methods in this class are the same as those for the OleDbDataReader and

OdbcDataReader classes

Table 9.2: SqlDataReader METHODS

METHOD RETURN

TYPE

DESCRIPTION

GetBoolean() bool Returns the value of the specified column as a bool GetByte() byte Returns the value of the specified column as a byte GetBytes() long Reads a stream of byte values from the specified

column into a byte array The long value returned is the number of byte values read from the column GetChar() char Returns the value of the specified column as a char GetChars() long Reads a stream of char values from the specified

column into a char array The long value returned is the number of char values read from the column GetDataTypeName() string Returns the name of the source data type for the

specified column

GetDateTime() DateTime Returns the value of the specified column as a

DateTime

GetDecimal() decimal Returns the value of the specified column as a

decimal

GetDouble() double Returns the value of the specified column as a

double

GetFieldType() Type Returns the Type of the specified column

GetFloat() float Returns the value of the specified column as a float GetGuid() Guid Returns the value of the specified column as a

globally unique identifier (GUID)

GetInt16() short Returns the value of the specified column as a short GetInt32() int Returns the value of the specified column as an int GetInt64() long Returns the value of the specified column as a long GetName() string Returns the name of the specified column

GetOrdinal() int Returns the numeric position, or ordinal, of the

specified column (first column has an ordinal of 0) GetSchemaTable() DataTable Returns a DataTable that contains details of the

columns stored in the data reader

GetSqlBinary() SqlBinary Returns the value of the specified column as a

SqlBinary object The SqlBinary class is declared in the System.Data.SqlTypes namespace

All the GetSql* methods are specific to the SqlDataReader class

GetSqlBoolean() SqlBoolean Returns the value of the specified column as a

SqlBoolean object

GetSqlByte() SqlByte Returns the value of the specified column as a

SqlByte object

GetSqlDateTime() SqlDateTime Returns the value of the specified column as a

SqlDateTime object

GetSqlDecimal() SqlDecimal Returns the value of the specified column as a

SqlDecimal object

GetSqlDouble() SqlDouble Returns the value of the specified column as a

SqlDouble object

GetSqlGuid() SqlGuid Returns the value of the specified column as a

SqlGuid object

GetSqlInt16() SqlInt16 Returns the value of the specified column as a

SqlInt16 object

GetSqlInt32() SqlInt32 Returns the value of the specified column as a

SqlInt32 object

GetSqlInt64() SqlInt64 Returns the value of the specified column as a

SqlInt64 object

GetSqlMoney() SqlMoney Returns the value of the specified column as a

SqlMoney object

GetSqlSingle() SqlSingle Returns the value of the specified column as a

SqlSingle object

GetSqlString() SqlString Returns the value of the specified column as a

SqlString object

GetSqlValue() object Returns the value of the specified column as an

object

GetSqlValues() int Copies the value of all the columns in the current

row into a specified object array The int returned

by this method is the number of elements in the array

GetString() string Returns the value of the specified column as a

string

GetValue() object Returns the value of the specified column as an

object

GetValues() int Copies the value of all the columns in the current

row into a specified object array The int returned

by this method is the number of elements in the array

IsDBNull() bool Returns a bool that indicates whether the specified

column contains a null value

NextResult() bool Moves the data reader to the next row in the result

set The bool returned by this method indicates whether there are more rows in the result set

Read() bool Moves the data reader to the next row in the result

set and reads the row The bool returned by this method indicates whether there are more rows in the result set

precision and scale of a numeric column (stored in NumericPrecision and

NumericScale), among others Precision is the total number of digits that make up a

number, and scale is the total number of digits to the right of the decimal point You saw how to read a schema using a program in the previous chapter

Tip The System.Data.SqlTypes namespace provides classes for native data types used

within SQL Server These classes provide a safer and faster alternative to other data

types returned by the other Get* methods Using the classes in this namespace helps

prevent type conversion errors caused by loss of precision Because other data types

are converted to and from SqlTypes behind the scenes, explicitly creating and using

objects within this namespace results in faster code as well You'll learn more about

the SqlTypes namespace later in the " Using the GetSql* Methods to Read Column