Belin.Sql

1.0.0

src/Cmdlets/Get-Scalar.psm1

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

<#
.SYNOPSIS
    Executes a parameterized SQL query that selects a single value.
.OUTPUTS
    The first column of the first row.
#>
function Get-Scalar {
    [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 object to return.
        [ValidateNotNull()]
        [Type] $As = [object]
    )

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

    end {
        $dbCommand = $Command.ToDbCommand($Connection, $Parameters)
        $value = $dbCommand.ExecuteScalar()
        ($null -eq $value) -or ($value -is [DBNull]) ? $null : [SqlMapper]::ChangeType($value, $As)
    }

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