$serviceName ="XYY.WindowsService.MQ";

function installService
{
    Write-Warning "安装服务";
    .\XYY.WindowsService.MQ install;
}
function uninstallService
{
    Write-Warning "卸载服务";
    .\XYY.WindowsService.MQ uninstall;
}

Get-Service $serviceName -ErrorAction SilentlyContinue;
if($?)
{
    Write-Output ($serviceName)"服务存在";
    uninstallService;
    installService;
}
else
{
    Write-Output ($serviceName)"服务不存在";
    installService;
}