UWP技术问询：如何修改RichEditBox文档的全部字体颜色？

Since you already have code working for modifying selected text's font color, scaling that to the whole document is super straightforward. Here are a couple of reliable approaches tailored for the UWP RichEditBox control:

Approach 1: Select All Text First (Simplest) #

This reuses the exact logic you already use for selected text—you just expand the selection to cover every character in the document first:

// Reference your RichEditBox instance
var targetRichEdit = yourRichEditBoxControl;

// Select the entire document content
targetRichEdit.Document.Selection.StartPosition = 0;
targetRichEdit.Document.Selection.EndPosition = targetRichEdit.Document.TextLength;

// Apply your desired font color (example uses dark red)
targetRichEdit.Document.Selection.CharacterFormat.ForegroundColor = Colors.DarkRed;

This mirrors the manual "select all + format" workflow you’d use yourself, so it’s intuitive and easy to integrate with your existing code.

Approach 2: Preserve the User’s Original Selection #

If you don’t want to disrupt the user’s current selected text while updating the whole document’s color, save the original selection bounds first, then restore them after formatting:

var targetRichEdit = yourRichEditBoxControl;

// Save the user's current selection positions
int originalSelectionStart = targetRichEdit.Document.Selection.StartPosition;
int originalSelectionEnd = targetRichEdit.Document.Selection.EndPosition;

// Format the entire document
targetRichEdit.Document.Selection.StartPosition = 0;
targetRichEdit.Document.Selection.EndPosition = targetRichEdit.Document.TextLength;
targetRichEdit.Document.Selection.CharacterFormat.ForegroundColor = Colors.DarkBlue;

// Restore the user's original selection
targetRichEdit.Document.Selection.StartPosition = originalSelectionStart;
targetRichEdit.Document.Selection.EndPosition = originalSelectionEnd;

Bonus: Set Default Color for New Text #

If you want any new text typed into the RichEditBox to automatically use your chosen color, set the default character format alongside updating existing content:

// Set default format for future input (new text will inherit this color)
targetRichEdit.Document.DefaultCharacterFormat.ForegroundColor = Colors.DarkGreen;

// Format existing content using either Approach 1 or 2 above

All these methods work without extra libraries or complex parsing—they leverage the built-in RichEditBox document APIs you’re already familiar with.

内容的提问来源于stack exchange，提问作者Seungbin Oh