test.cs

var loadedProperties;

using (TXTextControl.ServerTextControl tx = new TXTextControl.ServerTextControl())
{ 
    tx.Create();
    
    TXTextControl.LoadSettings loadSettings = new TXTextControl.LoadSettings();
    tx.Load(docFile, TXTextControl.StreamType.WordprocessingML, loadSettings);

    if (loadSettings.UserDefinedDocumentProperties != null)
    {
       loadedProperties = loadSettings.UserDefinedDocumentProperties;      
    }
}