Belin.Sql

1.0.0

src/Cmdlets/Get-Single.psm1

using namespace System.Data
using module ../SqlCommand.psm1
using module ../SqlMapper.psm1
using module ../SqlParameterCollection.psm1

<#
.SYNOPSIS
    Executes a parameterized SQL query and returns the single row.
.OUTPUTS
    The single row.
#>
function Get-Single {
    [CmdletBinding()]
    [OutputType([object])]
    param (
        # The connection to the data source.
        [Parameter(Mandatory, Position = 0)]
        [IDbConnection] $Connection,

        # The command to be executed.
        [Parameter(Mandatory, Position = 1)]
        [SqlCommand] $Command,

        # The parameters of the SQL statement.
        [Parameter(Position = 2)]
        [SqlParameterCollection] $Parameters,

        # The type of objects to return.
        [ValidateNotNull()]
        [Type] $As = [psobject]
    )

    begin {
        $dbCommand = $null
        $reader = $null
        if ($Connection.State -eq [ConnectionState]::Closed) { $Connection.Open() }
    }

    end {
        $dbCommand = $Command.ToDbCommand($Connection, $Parameters)
        $reader = $dbCommand.ExecuteReader()

        $rowCount = 0
        while ($reader.Read()) {
            if (++$rowCount -gt 1) { break }
            $record = [SqlMapper]::Instance.CreateInstance($As, $reader)
        }

        if ($rowCount -eq 1) { $record }
        else { Write-Error "The result set is empty or contains more than one record." -Category InvalidOperation }
    }

    clean {
        ${reader}?.Close()
        ${dbCommand}?.Dispose()
    }
}