picturebox breaking change (dotnet#41695)

Author: gewarren

docs/core/compatibility/9.0.md

@@ -56,6 +56,7 @@ If you're migrating an app to .NET 9, the breaking changes listed here might aff
 | [ComponentDesigner.Initialize throws ArgumentNullException](windows-forms/9.0/componentdesigner-initialize.md) | Behavioral change | Preview 1          |
 | [DataGridViewRowAccessibleObject.Name starting row index](windows-forms/9.0/datagridviewrowaccessibleobject-name-row.md) | Behavioral change | Preview 1 |
 | [No exception if DataGridView is null](windows-forms/9.0/datagridviewheadercell-nre.md) | Behavioral change   | Preview 1          |
+| [PictureBox raises HttpClient exceptions](windows-forms/9.0/httpclient-exceptions.md)   | Behavioral change   | Preview 6          |
 
 ## WPF
 

docs/core/compatibility/toc.yml

@@ -52,6 +52,8 @@ items:
         href: windows-forms/9.0/datagridviewrowaccessibleobject-name-row.md
       - name: No exception if DataGridView is null
         href: windows-forms/9.0/datagridviewheadercell-nre.md
+      - name: PictureBox raises HttpClient exceptions
+        href: windows-forms/9.0/httpclient-exceptions.md
     - name: WPF
       items:
       - name: "'GetXmlNamespaceMaps' type change"
@@ -1832,6 +1834,8 @@ items:
         href: windows-forms/9.0/datagridviewrowaccessibleobject-name-row.md
       - name: No exception if DataGridView is null
         href: windows-forms/9.0/datagridviewheadercell-nre.md
+      - name: PictureBox raises HttpClient exceptions
+        href: windows-forms/9.0/httpclient-exceptions.md
     - name: .NET 8
       items:
       - name: Anchor layout changes

docs/core/compatibility/windows-forms/9.0/httpclient-exceptions.md

@@ -0,0 +1,36 @@
+---
+title: "Breaking change: PictureBox raises HttpClient exceptions"
+description: Learn about the breaking change in .NET 9 for Windows Forms where `PictureBox` raises HttpClient exceptions for network errors when loading an image from a URL.
+ms.date: 07/09/2024
+---
+# PictureBox raises HttpClient exceptions
+
+When <xref:System.Windows.Forms.PictureBox> loads an image from a URL and a network error occurs, it now raises <xref:System.Net.Http.HttpClient> exceptions, such as <xref:System.Net.Http.HttpRequestException> and <xref:System.Threading.Tasks.TaskCanceledException>, instead of <xref:System.Net.WebException>.
+
+## Version introduced
+
+.NET 9 Preview 6
+
+## Previous behavior
+
+Previously, when <xref:System.Windows.Forms.PictureBox> failed to load an image from a URL due to a network error, a <xref:System.Net.WebException> was thrown.
+
+## New behavior
+
+Starting in .NET 9, when <xref:System.Windows.Forms.PictureBox> fails to load an image from a URL due to a network error, <xref:System.Net.Http.HttpRequestException> or <xref:System.Threading.Tasks.TaskCanceledException> is thrown.
+
+## Change category
+
+This change is a [*behavioral change*](../../categories.md#behavioral-change).
+
+## Reason for change
+
+<xref:System.Net.WebClient> is obsolete.
+
+## Recommended action
+
+Update your code to catch <xref:System.Net.Http.HttpRequestException> and <xref:System.Threading.Tasks.TaskCanceledException> instead of <xref:System.Net.WebException>.
+
+## Affected APIs
+
+- <xref:System.Windows.Forms.PictureBox> control