diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs b/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs
index 5a81f4ccf70..02fb8d840b0 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/Control.cs
@@ -7803,15 +7803,16 @@ private void OnSetScrollPosition(object sender, EventArgs e)
             OnInvokedSetScrollPosition(sender, e);
         }
 
-        internal virtual void OnInvokedSetScrollPosition(object sender, EventArgs e)
+        internal unsafe virtual void OnInvokedSetScrollPosition(object sender, EventArgs e)
         {
             if (!(this is ScrollableControl) && !IsMirrored)
             {
-                var si = new User32.SCROLLINFO
+                User32.SCROLLINFO si = new()
                 {
-                    cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                    cbSize = (uint)sizeof(User32.SCROLLINFO),
                     fMask = User32.SIF.RANGE
                 };
+
                 if (User32.GetScrollInfo(this, User32.SB.HORZ, ref si).IsTrue())
                 {
                     si.nPos = (RightToLeft == RightToLeft.Yes) ? si.nMax : si.nMin;
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/Printing/PrintPreviewControl.cs b/src/System.Windows.Forms/src/System/Windows/Forms/Printing/PrintPreviewControl.cs
index 625f063dd78..3481afd455d 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/Printing/PrintPreviewControl.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/Printing/PrintPreviewControl.cs
@@ -310,17 +310,18 @@ public double Zoom
             }
         }
 
-        private int AdjustScroll(Message m, int pos, int maxPos, bool horizontal)
+        private unsafe int AdjustScroll(Message m, int pos, int maxPos, bool horizontal)
         {
             switch ((User32.SBH)PARAM.LOWORD(m.WParam))
             {
                 case User32.SBH.THUMBPOSITION:
                 case User32.SBH.THUMBTRACK:
-                    var si = new User32.SCROLLINFO
+                    User32.SCROLLINFO si = new()
                     {
-                        cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                        cbSize = (uint)sizeof(User32.SCROLLINFO),
                         fMask = User32.SIF.TRACKPOS
                     };
+
                     User32.SB direction = horizontal ? User32.SB.HORZ : User32.SB.VERT;
                     if (User32.GetScrollInfo(m.HWnd, direction, ref si).IsTrue())
                     {
@@ -745,19 +746,20 @@ private void SetPositionNoInvalidate(Point value)
             User32.SetScrollPos(this, User32.SB.VERT, position.Y, BOOL.TRUE);
         }
 
-        internal void SetVirtualSizeNoInvalidate(Size value)
+        internal unsafe void SetVirtualSizeNoInvalidate(Size value)
         {
             virtualSize = value;
             SetPositionNoInvalidate(position); // Make sure it's within range
 
-            var info = new User32.SCROLLINFO
+            User32.SCROLLINFO info = new()
             {
-                cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                cbSize = (uint)sizeof(User32.SCROLLINFO),
                 fMask = User32.SIF.RANGE | User32.SIF.PAGE,
                 nMin = 0,
                 nMax = Math.Max(Height, virtualSize.Height) - 1,
                 nPage = (uint)Height
             };
+
             User32.SetScrollInfo(this, User32.SB.VERT, ref info, BOOL.TRUE);
 
             info.fMask = User32.SIF.RANGE | User32.SIF.PAGE;
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollBar.cs b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollBar.cs
index 1e7a560672f..1a7e7259e1c 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollBar.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollBar.cs
@@ -587,33 +587,35 @@ public override string ToString()
             return s + ", Minimum: " + Minimum + ", Maximum: " + Maximum + ", Value: " + Value;
         }
 
-        protected void UpdateScrollInfo()
+        protected unsafe void UpdateScrollInfo()
         {
-            if (IsHandleCreated && Enabled)
+            if (!IsHandleCreated || !Enabled)
             {
-                var si = new User32.SCROLLINFO
-                {
-                    cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
-                    fMask = User32.SIF.ALL,
-                    nMin = _minimum,
-                    nMax = _maximum,
-                    nPage = (uint)LargeChange
-                };
-
-                if (RightToLeft == RightToLeft.Yes)
-                {
-                    // Reflect the scrollbar position horizontally on an Rtl system
-                    si.nPos = ReflectPosition(_value);
-                }
-                else
-                {
-                    si.nPos = _value;
-                }
+                return;
+            }
 
-                si.nTrackPos = 0;
+            User32.SCROLLINFO si = new()
+            {
+                cbSize = (uint)sizeof(User32.SCROLLINFO),
+                fMask = User32.SIF.ALL,
+                nMin = _minimum,
+                nMax = _maximum,
+                nPage = (uint)LargeChange
+            };
 
-                User32.SetScrollInfo(this, User32.SB.CTL, ref si, BOOL.TRUE);
+            if (RightToLeft == RightToLeft.Yes)
+            {
+                // Reflect the scrollbar position horizontally on an Rtl system
+                si.nPos = ReflectPosition(_value);
+            }
+            else
+            {
+                si.nPos = _value;
             }
+
+            si.nTrackPos = 0;
+
+            User32.SetScrollInfo(this, User32.SB.CTL, ref si, BOOL.TRUE);
         }
 
         private void WmReflectScroll(ref Message m)
@@ -622,7 +624,7 @@ private void WmReflectScroll(ref Message m)
             DoScroll(type);
         }
 
-        private void DoScroll(ScrollEventType type)
+        private unsafe void DoScroll(ScrollEventType type)
         {
             // For Rtl systems we need to swap increment and decrement
             if (RightToLeft == RightToLeft.Yes)
@@ -689,11 +691,12 @@ private void DoScroll(ScrollEventType type)
 
                 case ScrollEventType.ThumbPosition:
                 case ScrollEventType.ThumbTrack:
-                    var si = new User32.SCROLLINFO
+                    User32.SCROLLINFO si = new()
                     {
-                        cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                        cbSize = (uint)sizeof(User32.SCROLLINFO),
                         fMask = User32.SIF.TRACKPOS
                     };
+
                     User32.GetScrollInfo(this, User32.SB.CTL, ref si);
 
                     if (RightToLeft == RightToLeft.Yes)
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollProperties.cs b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollProperties.cs
index 380a06eaddc..694ba1057d8 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollProperties.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollProperties.cs
@@ -269,13 +269,13 @@ public bool Visible
             }
         }
 
-        internal void UpdateScrollInfo()
+        internal unsafe void UpdateScrollInfo()
         {
             if (_parent is not null && _parent.IsHandleCreated && _visible)
             {
-                var si = new User32.SCROLLINFO
+                User32.SCROLLINFO si = new()
                 {
-                    cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                    cbSize = (uint)sizeof(User32.SCROLLINFO),
                     fMask = User32.SIF.ALL,
                     nMin = _minimum,
                     nMax = _maximum,
@@ -283,6 +283,7 @@ internal void UpdateScrollInfo()
                     nPos = _value,
                     nTrackPos = 0
                 };
+
                 User32.SetScrollInfo(_parent, Orientation, ref si, BOOL.TRUE);
             }
         }
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollableControl.cs b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollableControl.cs
index 10fb414848c..8deb09da35c 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/ScrollableControl.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/ScrollableControl.cs
@@ -927,13 +927,14 @@ protected virtual Point ScrollToControl(Control activeControl)
             return new Point(xCalc, yCalc);
         }
 
-        private int ScrollThumbPosition(User32.SB fnBar)
+        private unsafe int ScrollThumbPosition(User32.SB fnBar)
         {
-            var si = new User32.SCROLLINFO
+            User32.SCROLLINFO si = new()
             {
-                cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                cbSize = (uint)sizeof(User32.SCROLLINFO),
                 fMask = User32.SIF.TRACKPOS
             };
+
             User32.GetScrollInfo(this, fnBar, ref si);
             return si.nTrackPos;
         }
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/TreeView.cs b/src/System.Windows.Forms/src/System/Windows/Forms/TreeView.cs
index d194c797efa..aa31afbb54c 100644
--- a/src/System.Windows.Forms/src/System/Windows/Forms/TreeView.cs
+++ b/src/System.Windows.Forms/src/System/Windows/Forms/TreeView.cs
@@ -2778,11 +2778,12 @@ private unsafe void CustomDraw(ref Message m)
                         {
                             Rectangle bounds = node.RowBounds;
 
-                            var si = new User32.SCROLLINFO
+                            User32.SCROLLINFO si = new()
                             {
-                                cbSize = (uint)Marshal.SizeOf<User32.SCROLLINFO>(),
+                                cbSize = (uint)sizeof(User32.SCROLLINFO),
                                 fMask = User32.SIF.POS
                             };
+
                             if (User32.GetScrollInfo(this, User32.SB.HORZ, ref si).IsTrue())
                             {
                                 // need to get the correct bounds if horizontal scroll bar is shown.