The WPF binding infrastructure updates the source object whenever the DP is set even if it is to the same value. When you go into edit mode, the editor recalculates the text property by reconverting the value to a string since you could have a displaytextconverter that represents the value differently while in edit mode then not. You could either set the IsAlwaysInEditMode to true so that it doesn't enter/leave edit mode based on focus or bind the Value property instead of binding the Text property.