It appears you are trying to have the XML file indicate to the system that it should keep the same value that exists. Is that right?
If so, you aren't actually changing the value in the field and therefore no change would be committed and the above rule wouldn't run.
If you have your new import settings set up how you want it in the future then I suggest you use a workflow and a Run for Search workflow block to make corrections to records that aren't reflecting properly at the moment. There's a KB article that covers a similar situation where the "Supervisor" field isn't updated correctly when that linked record's Display name is changed. You could likely simplify and adapt this method to meet your need:
thank you for your answer.
The Values in XML File should Update and Create new records. Also new Records which are created have not filled out the "middlename" field. All new Records have a Comma "," in Displayname Field, because First, Last and Middlename Fields are empty. This fields i want to fill out. But the import did not fill it out.
I'm not sure I understand. Perhaps you can share a sample of the data you are importing, your import settings, and the resulting Contact record?
Also, as I look at these lines from your original post I'm wondering if there's and XSLT transformation involved here as well?
thank you for the Response. Ive solved the Problem. I could not Import the Value of XML File because the Fieldname was Case Sensitive :-D
I corrected Field Name to "LastName" and the Import worked.
Big Thx anyway :-)