edmx-extract.ps1

<#
    .NOTES
        Licensed under WTFPL, Version 2.
    .SYNOPSIS
        Extracts the DB-schema from the latest EF migration in the specified database.
    .DESCRIPTION
        Writes the extracted schema to the output file in the EDMX format.
        The "(local)" server is used.
    .PARAMETER Database
        The database with EF migrations (in the __MigrationHistory table).
    .PARAMETER OutFile
        The file to write the schema to.
    .LINK
        Depends on the SQLPS module, see
        http://guidestomicrosoft.com/2015/01/13/install-sql-server-powershell-module-sqlps/
    .Example
        .\edmx-extract.ps1 -Database my_db -OutFile schema.edmx
#>
param (
    [parameter(mandatory=$true)][string]$Database,
    [parameter(mandatory=$false)][string]$OutFile = $null
)

Push-Location
Import-Module sqlps -DisableNameChecking
Pop-Location

$sizeResult = Invoke-Sqlcmd -ServerInstance "(local)" -Database $Database -Query @"
SELECT TOP 1
		DATALENGTH([Model]) as Size
FROM [__MigrationHistory]
ORDER BY MigrationId DESC
"@

$size = $sizeResult.Size

$x = Invoke-Sqlcmd -MaxBinaryLength $size -ServerInstance "(local)" -Database $Database -Query @"
SELECT TOP 1
		[MigrationId]
		,[ContextKey]
		,[Model]
		,[ProductVersion]
FROM [__MigrationHistory]
ORDER BY MigrationId DESC
"@

if (-not $OutFile) {
    $OutFile = "$($x.MigrationId).edmx"
}

[System.IO.Directory]::SetCurrentDirectory(((Get-Location -PSProvider FileSystem).ProviderPath))
$OutFile = [IO.Path]::GetFullPath($OutFile)

$bytes = $x.Model
$inp = New-Object System.IO.MemoryStream ($bytes, $false)
$output = New-Object System.IO.FileStream $OutFile, ([IO.FileMode]::Create), ([IO.FileAccess]::Write), ([IO.FileShare]::None)
$gzipStream = New-Object System.IO.Compression.GzipStream $inp, ([IO.Compression.CompressionMode]::Decompress)
try {
    $buffer = New-Object byte[](1024);
    while ($true) {
        $read = $gzipStream.Read($buffer, 0, 1024)
        if ($read -le 0) {
            break;
        }
        $output.Write($buffer, 0, $read)
    }
}
finally {
    Write-Verbose "Closing streams and newly decompressed file"
    $gzipStream.Close();
    $output.Close();
    $inp.Close();
}