From 9c36d93329eaa4b992571cb9bb9fc66a4ef77aa9 Mon Sep 17 00:00:00 2001
From: tian-lt <tilia@microsoft.com>
Date: Tue, 15 Jun 2021 10:49:02 +0800
Subject: [PATCH] fixes: GraphingNumber doesn't work correctly

---
 src/Calculator/Controls/MathRichEditBox.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Calculator/Controls/MathRichEditBox.cs b/src/Calculator/Controls/MathRichEditBox.cs
index 23966eb3..ce642790 100644
--- a/src/Calculator/Controls/MathRichEditBox.cs
+++ b/src/Calculator/Controls/MathRichEditBox.cs
@@ -137,7 +137,7 @@ namespace CalculatorApp
                 // If the rich edit has content already, then the mathzone will already be created due to mathonly mode being set and the selection will exist inside the
                 // math zone. To handle this, we will force a math zone to be created in teh case of the text being empty and then replacing the text inside of the math
                 // zone with the newly inserted text.
-                if (GetMathTextProperty() == null)
+                if (string.IsNullOrEmpty(GetMathTextProperty()))
                 {
                     SetMathTextProperty("<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>x</mi></math>");
                     TextDocument.Selection.StartPosition = 0;