Bugfix: Crash while saving when hosts was disabled and enabled together

src/HostsFile.cs

@@ -182,6 +182,11 @@ public int LineCount
             }
         }
 
+        /// <summary>
+        /// Gets value indicating if the HostsFile is currently disabled.
+        /// </summary>
+        public static bool IsDisabled => File.Exists(DefaultDisabledHostFilePath);
+
         #endregion
 
         #region Public Methods
@@ -191,6 +196,11 @@ public int LineCount
         /// </summary>
         public static void DisableHostsFile()
         {
+            if (IsEnabled && IsDisabled)
+            {
+                throw new InvalidOperationException("The HostsFile is enabled and disabled at the same time.");
+            }
+
             using (FileEx.DisableAttributes(DefaultHostFilePath, FileAttributes.ReadOnly))
             {
                 File.Move(DefaultHostFilePath, DefaultDisabledHostFilePath);
@@ -203,6 +213,11 @@ public static void DisableHostsFile()
         /// </summary>
         public static void EnableHostsFile()
         {
+            if (IsEnabled && IsDisabled)
+            {
+                throw new InvalidOperationException("The HostsFile is enabled and disabled at the same time.");
+            }
+
             using (FileEx.DisableAttributes(DefaultDisabledHostFilePath, FileAttributes.ReadOnly))
             {
                 File.Move(DefaultDisabledHostFilePath, DefaultHostFilePath);

src/MainForm.cs

@@ -312,11 +312,31 @@ private void OnDisableHostsClick(object sender, EventArgs e)
 
             if (checkState)
             {
-                HostsFile.EnableHostsFile();
+                try
+                {
+                    HostsFile.EnableHostsFile();
+                }
+                catch (InvalidOperationException invalidOperationException)
+                {
+                    Console.WriteLine(invalidOperationException);
+                    MessageBox.Show(invalidOperationException.Message, "Error during operation!", MessageBoxButtons.OK,
+                        MessageBoxIcon.Error);
+                    return;
+                }
             }
             else
             {
-                HostsFile.DisableHostsFile();
+                try
+                {
+                    HostsFile.DisableHostsFile();
+                }
+                catch (InvalidOperationException invalidOperationException)
+                {
+                    Console.WriteLine(invalidOperationException);
+                    MessageBox.Show(invalidOperationException.Message, "Error during operation!", MessageBoxButtons.OK,
+                        MessageBoxIcon.Error);
+                    return;
+                }
             }
 
             this.UpdateNotifyIcon();
@@ -614,6 +634,12 @@ private void OnSaveClick(object sender, EventArgs e)
             this.dataGridViewHostsEntries.CommitEdit(
                 DataGridViewDataErrorContexts.Commit);
 
+            if (HostsFile.IsDisabled)
+            {
+                MessageBox.Show("The HostsFile is currently disabled. Enable the HostsFile before editing entries.");
+                return;
+            }
+
             HostsFile.Instance.Save();
         }