Fix compile errors on net6.0.

src/Markup/Avalonia.Markup/Markup/Data/DelayedBinding.cs

@@ -38,7 +38,7 @@ namespace Avalonia.Markup.Data
             else
             {
 
-                if (!_entries.TryGetValue(target, out List<Entry> bindings))
+                if (!_entries.TryGetValue(target, out var bindings))
                 {
                     bindings = new List<Entry>();
                     _entries.Add(target, bindings);
@@ -65,9 +65,7 @@ namespace Avalonia.Markup.Data
             }
             else
             {
-                List<Entry> bindings;
-
-                if (!_entries.TryGetValue(target, out bindings))
+                if (!_entries.TryGetValue(target, out var bindings))
                 {
                     bindings = new List<Entry>();
                     _entries.Add(target, bindings);
@@ -86,9 +84,7 @@ namespace Avalonia.Markup.Data
         /// <param name="control">The control.</param>
         public static void ApplyBindings(IStyledElement control)
         {
-            List<Entry> entries;
-
-            if (_entries.TryGetValue(control, out entries))
+            if (_entries.TryGetValue(control, out var entries))
             {
                 foreach (var entry in entries)
                 {

src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs

@@ -215,7 +215,7 @@ namespace Avalonia.Markup.Parsers.Nodes
             return AvaloniaProperty.UnsetValue;
         }
 
-        private object GetValueFromArray(Array array)
+        private object? GetValueFromArray(Array array)
         {
             int[] intArgs;
             if (!ConvertArgumentsToInts(out intArgs))
@@ -223,7 +223,7 @@ namespace Avalonia.Markup.Parsers.Nodes
             return GetValueFromArray(array, intArgs);
         }
 
-        private object GetValueFromArray(Array array, int[] indices)
+        private object? GetValueFromArray(Array array, int[] indices)
         {
             if (ValidBounds(indices, array))
             {
@@ -258,7 +258,7 @@ namespace Avalonia.Markup.Parsers.Nodes
             {
                 // Check for the default indexer name first to make this faster.
                 // This will only be false when a class in VB has a custom indexer name.
-                if ((indexer = typeInfo.GetDeclaredProperty(CommonPropertyNames.IndexerName)) != null)
+                if ((indexer = typeInfo.GetDeclaredProperty(CommonPropertyNames.IndexerName)!) != null)
                 {
                     return indexer;
                 }

src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs

@@ -4,7 +4,6 @@ using System.ComponentModel;
 using System.IO;
 using System.Reflection;
 using System.Runtime.InteropServices;
-using System.Runtime.InteropServices.WindowsRuntime;
 using System.Threading;
 using Avalonia.MicroCom;
 using Avalonia.Win32.Interop;