From d7ca28a443113a541769d3768747fc8641a10faa Mon Sep 17 00:00:00 2001
From: Deadpikle <mbabienco@southern.edu>
Date: Sun, 5 Apr 2020 11:28:54 -0400
Subject: [PATCH 1/3] Add failing test for clearing SelectedText

---
 .../TextBoxTests.cs                            | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
index 7f24a57678..f47aa915c9 100644
--- a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
@@ -425,6 +425,24 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void SelectedText_CanClearText()
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var target = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "0123"
+                };
+                target.SelectionStart = 1;
+                target.SelectionEnd = 3;
+                target.SelectedText = "";
+
+                Assert.True(target.Text == "03");
+            }
+        }
+
         [Fact]
         public void CoerceCaretIndex_Doesnt_Cause_Exception_with_malformed_line_ending()
         {

From 14b227037b929abea8878a3a8f8911186560eaaa Mon Sep 17 00:00:00 2001
From: Deadpikle <mbabienco@southern.edu>
Date: Sun, 5 Apr 2020 11:42:48 -0400
Subject: [PATCH 2/3] Delete selection if SelectedText = ""

---
 src/Avalonia.Controls/TextBox.cs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index d25649f2a1..2920e3a5cf 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -283,7 +283,14 @@ namespace Avalonia.Controls
                 }
 
                 _undoRedoHelper.Snapshot();
-                HandleTextInput(value);
+                if (value != "")
+                {
+                    HandleTextInput(value);
+                }
+                else
+                {
+                    DeleteSelection();
+                } 
                 _undoRedoHelper.Snapshot();
             }
         }

From 681911098c2f5ff2234e58f87936b560313b9610 Mon Sep 17 00:00:00 2001
From: Deadpikle <mbabienco@southern.edu>
Date: Mon, 6 Apr 2020 17:16:51 -0400
Subject: [PATCH 3/3] SelectedText = null -> clear text

---
 src/Avalonia.Controls/TextBox.cs               | 11 +++--------
 .../TextBoxTests.cs                            | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index 2920e3a5cf..680d7e7d2b 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -277,19 +277,14 @@ namespace Avalonia.Controls
             get { return GetSelection(); }
             set
             {
-                if (value == null)
-                {
-                    return;
-                }
-
                 _undoRedoHelper.Snapshot();
-                if (value != "")
+                if (string.IsNullOrEmpty(value))
                 {
-                    HandleTextInput(value);
+                    DeleteSelection();
                 }
                 else
                 {
-                    DeleteSelection();
+                    HandleTextInput(value);
                 } 
                 _undoRedoHelper.Snapshot();
             }
diff --git a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
index f47aa915c9..6bb3d55799 100644
--- a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
@@ -443,6 +443,24 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void SelectedText_NullClearsText()
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var target = new TextBox
+                {
+                    Template = CreateTemplate(),
+                    Text = "0123"
+                };
+                target.SelectionStart = 1;
+                target.SelectionEnd = 3;
+                target.SelectedText = null;
+
+                Assert.True(target.Text == "03");
+            }
+        }
+
         [Fact]
         public void CoerceCaretIndex_Doesnt_Cause_Exception_with_malformed_line_ending()
         {