You can use SQL for WMI WHERE clause queries, something like this:

var searcher = new ManagementObjectSearcher(
                   @"ROOT\StandardCimv2\embedded",
                   @"SELECT * FROM UWF_Servicing WHERE CurrentSession = FALSE");
foreach (ManagementObject obj in searcher.Get())
{
    ... etc ...
}

But you can also use the object's properties (values types will map to standard .NET's types), like this:

var searcher = new ManagementObjectSearcher(
                   @"ROOT\StandardCimv2\embedded",
                   @"SELECT * FROM UWF_Servicing");
foreach (ManagementObject obj in searcher.Get())
{
    var currentSession = obj.GetPropertyValue("CurrentSession");
    if (false.Equals(currentSession))
    {
        ... etc ...
    }
}