Replacing the word in the Word template is equivalent to modifying the word content (saving the original word style)

// Replacing the word in the Word template is equivalent to modifying the word content.
Private void wordreplace (string filepath, string strold, string strnew)
{
Microsoft. Office. InterOP. Word. _ application APP = new Microsoft. Office. InterOP. Word. applicationclass ();
Object nullobj = system. reflection. Missing. value;
Object File = filepath;
Microsoft. Office. InterOP. Word. _ document DOC = app. Documents. Open (
Ref file, ref nullobj, ref nullobj,
Ref nullobj, ref nullobj, ref nullobj,
Ref nullobj, ref nullobj, ref nullobj,
Ref nullobj, ref nullobj, ref nullobj,
Ref nullobj, ref nullobj) as Microsoft. Office. InterOP. Word. _ document;

App. selection. Find. clearformatting ();
App. selection. Find. Replacement. clearformatting ();
App. selection. Find. Text = strold;
App. selection. Find. Replacement. Text = strnew;

Object objreplace = Microsoft. Office. InterOP. Word. wdreplace. wdreplaceall;
App. selection. Find. Execute (ref nullobj,
Ref nullobj, ref nullobj, ref nullobj,
Ref nullobj, ref nullobj, ref nullobj,
Ref nullobj, ref objreplace, ref nullobj,
Ref nullobj, ref nullobj, ref nullobj );

// Format
// Doc. content. AutoFormat ();
// Clear the range object
// Microsoft. Office. InterOP. Word. range = NULL;

// Save
Doc. Save ();

// Microsoft. Office. InterOP. Word. range = NULL;
Doc. Close (ref nullobj, ref nullobj, ref nullobj );

App. Quit (ref nullobj, ref nullobj, ref nullobj );
}