SqlCeDataReader.Seek Method

Places the SqlCeDataReader on the record with indexed values that match the specified parameters.

Namespace: System.Data.SqlServerCe
Assembly: System.Data.SqlServerCe (in system.data.sqlserverce.dll)

Syntax

'Declaration
Public Function Seek ( _
    dbSeekOptions As DbSeekOptions, _
    ParamArray index As Object() _
) As Boolean

public bool Seek (
    DbSeekOptions dbSeekOptions,
    params Object[] index
)

public:
bool Seek (
    DbSeekOptions dbSeekOptions, 
    ... array<Object^>^ index
)

public boolean Seek (
    DbSeekOptions dbSeekOptions, 
    Object[] index
)

public function Seek (
    dbSeekOptions : DbSeekOptions, 
    ... index : Object[]
) : boolean

Parameters

• dbSeekOptions
  The DbSeekOptions to use.

• index
  The index of the record.

Return Value

A Boolean value; true indicates the cursor is positioned on a row.

Exceptions

Remarks

This method is intended to be a faster alternative to a SELECT statement for retrieving a row from a base table. Instead of a WHERE clause in a SELECT statement, Seek can be used to quickly retrieve a row based on its index value. For example, to retrieve an employee with an employee ID of 5, you could execute a SELECT statement, but using Seek with a value of 5 on the employee ID index will greatly improve performance.

Seek can only be used when CommandType is set to TableDirect, CommandText is set to a valid base table name, and IndexName is set to a valid index name on the specified base table.

After using Seek, SqlCeDataReader will return the remaining rows in their index order. When Seek is used on a SqlCeDataReader that has a range specified by SetRange, Seek will only position on rows within the range. For more information, see the "IRowsetIndex::Seek" topic in the OLE DB documentation.

Example

Try
    Dim conn As New SqlCeConnection("Data Source = MyDatabase.sdf")
    conn.Open()

    Dim cmd As SqlCeCommand = conn.CreateCommand()
    cmd.CommandType = CommandType.TableDirect
    cmd.IndexName = "Orders_PK"
    cmd.CommandText = "Orders"

    ' We are interested in orders that match Order ID = 10020
    '
    cmd.SetRange(DbRangeOptions.Match, New Object() {10020}, Nothing)

    Dim reader As SqlCeDataReader = cmd.ExecuteReader(CommandBehavior.Default)

    While reader.Read()
        MessageBox.Show(String.Format("{0} ; {1}", reader("Order ID"), reader("Order Date")))
    End While

    ' Now we are interested in orders with Order ID between (10020, 10050)
    '
    cmd.SetRange(DbRangeOptions.InclusiveStart Or DbRangeOptions.InclusiveEnd, New Object() {10020}, New Object() {10050})

    reader = cmd.ExecuteReader(CommandBehavior.Default)

    ' Now seek to Order ID = 10045
    '
    Dim onRow As Boolean =  reader.Seek(DbSeekOptions.FirstEqual, New Object() {10045})

    ' Now ,the reader will return rows with Order ID >= 10045 <= 10050
    ' because the range was set to (10020, 10050)
    '
    If onRow Then
        While reader.Read()
            MessageBox.Show(String.Format("{0} ; {1}", reader("Order ID"), reader("Order Date")))
        End While
    End If
Catch e As Exception
    MessageBox.Show(e.Message)
End Try

try
{
    SqlCeConnection conn = new SqlCeConnection("Data Source = MyDatabase.sdf");
    conn.Open();

    SqlCeCommand cmd = conn.CreateCommand();
    cmd.CommandType = CommandType.TableDirect;
    cmd.IndexName = "Orders_PK";
    cmd.CommandText = "Orders";

    // We are interested in orders that match Order ID = 10020
    //
    cmd.SetRange(DbRangeOptions.Match, new object[] { 10020 }, null);

    SqlCeDataReader reader = cmd.ExecuteReader(CommandBehavior.Default);

    for (int i = 1; reader.Read(); i++)
    {
        MessageBox.Show(String.Format("{0} ; {1}", reader["Order ID"], reader["Order Date"]));
    }

    // Now we are interested in orders with Order ID between (10020, 10050)
    //
    cmd.SetRange(DbRangeOptions.InclusiveStart | DbRangeOptions.InclusiveEnd,
        new object[] { 10020 }, new object[] { 10050 });

    reader = cmd.ExecuteReader(CommandBehavior.Default);

    // Now seek to Order ID = 10045
    //
    bool onRow = reader.Seek(DbSeekOptions.FirstEqual, new object[] { 10045 });

    // Now ,the reader will return rows with Order ID >= 10045 <= 10050
    // because the range was set to (10020, 10050)
    //
    if (onRow)
    {
        for (int i = 1; reader.Read(); i++)
        {
            MessageBox.Show(String.Format("{0} ; {1}", reader["Order ID"], reader["Order Date"]));
        }
    }
}
catch (Exception e)
{
    MessageBox.Show(e.Message);
}

Thread Safety

Any public static (Shared in Microsoft Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Platforms

Development Platforms

Windows Vista, Windows Mobile 5.0, Windows XP Professional with Service Pack 2 (SP2), Windows Server 2003, Windows Mobile 2003 for Pocket PC, Windows CE 5.0
Version Information
.NET Framework and NET Compact Framework
Supported in 3.5
.NET Framework
Supported in 3.0
.NET Compact Framework and .Net Framework
Supported in 2.0

See Also

Reference

SqlCeDataReader Class
SqlCeDataReader Members
System.Data.SqlServerCe Namespace