Functions/Test-User.ps1

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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

function Test-User
{
    <#
    .SYNOPSIS
    Checks if a *local* user account exists.
 
    .DESCRIPTION
    Uses .NET's AccountManagement API to check if a *local* user account exists. Returns `True` if the *local* account exists, or `False` if it doesn't.
 
    .OUTPUTS
    System.Boolean
 
    .LINK
    Get-User
 
    .LINK
    Install-User
 
    .LINK
    Uninstall-User
 
    .EXAMPLE
    Test-User -Username HSolo
 
    Checks if the HSolo *local* account exists. Returns `True` if it does, `False` if it doesn't or its encased in carbonite.
    #>

    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true)]
        [ValidateLength(1,20)]
        [string]
        # The username of the *local* account to check
        $Username
    )

    Set-StrictMode -Version 'Latest'

    Use-CallerPreference -Cmdlet $PSCmdlet -Session $ExecutionContext.SessionState
    
    $ctx = New-Object 'DirectoryServices.AccountManagement.PrincipalContext' ([DirectoryServices.AccountManagement.ContextType]::Machine)
    $user = [DirectoryServices.AccountManagement.UserPrincipal]::FindByIdentity( $ctx, $Username )
    if( $user )
    {
        return $true
    }
    else
    {
        try
        {
            return $false
        }
        finally
        {
            $ctx.Dispose()
        }
    }
}