Merge pull request #4 from SyncfusionExamples/WF-64663-ComboBoxDropDown

WF-64663-Changed ReadMe file

Author: Manivannan-E

README.md

@@ -1,2 +1,71 @@
-# how-to-disable-some-items-winforms-combobox-dropdown
-This sample shows how to disable some items winforms combobox dropdown.
+# How to Disable Items in WinForms ComboBox Dropdown
+## Overview
+This example demonstrates how to disable specific items in a WinForms ComboBox dropdown using Syncfusion's SfComboBox control. This is useful when you want to prevent users from selecting certain items based on business logic or application state.
+
+## Changing ForeColor for Disabled Items
+You can visually indicate disabled items by customizing their appearance using the DrawItem event of DropDownListView.
+### C# Example
+```C#
+sfComboBox.DropDownListView.DrawItem += DropDownListView_DrawItem;
+
+private void DropDownListView_DrawItem(object sender, Syncfusion.WinForms.ListView.Events.DrawItemEventArgs e)
+{
+    bool isItemEnable = (sfComboBox.ComboBoxMode == ComboBoxMode.MultiSelection &&
+                         sfComboBox.AllowSelectAll &&
+                         e.ItemIndex == 0)
+                         ? true
+                         : (e.ItemData as Details).IsEnabled;
+
+    if (!isItemEnable)
+    {
+        e.Style.BackColor = Color.LightGray;
+        e.Style.ForeColor = Color.Gray;
+    }
+}
+```
+
+## Handling Selection for Disabled Items
+Selection logic differs based on whether the ComboBox is in multi-selection or single-selection mode.
+### Multi-Selection Mode:
+```C#
+private void DropDownListView_SelectionChanged(object sender, ItemSelectionChangedEventArgs e)
+{
+    if (e.AddedItems.Count == sfComboBox.DropDownListView.View.Items.Count)
+    {
+        for (int i = 0; i < sfComboBox.DropDownListView.CheckedItems.Count; i++)
+        {
+            if (!(sfComboBox.DropDownListView.CheckedItems[i] as Details).IsEnabled)
+                sfComboBox.DropDownListView.CheckedItems.RemoveAt(i);
+        }
+    }
+}
+
+private void DropDownListView_ItemChecking(object sender, ItemCheckingEventArgs e)
+{
+    bool isItemEnable = (sfComboBox.ComboBoxMode == ComboBoxMode.MultiSelection &&
+                         sfComboBox.AllowSelectAll &&
+                         e.ItemIndex == 0)
+                         ? true
+                         : (e.ItemData as Details).IsEnabled;
+
+    if (!isItemEnable)
+        e.Cancel = true;
+}
+```
+### Single-Selection Mode
+```C#
+private void DropDownListView_SelectionChanging(object sender, ItemSelectionChangingEventArgs e)
+{
+    if (e.AddedItems.Count > 0 &&
+        !(e.AddedItems[0] as Details).IsEnabled &&
+        e.AddedItems.Count != sfComboBox.DropDownListView.View.Items.Count)
+    {
+        e.Cancel = true;
+    }
+}
+```
+## Reference
+For detailed guidance and step-by-step instructions, refer to the official Syncfusion Knowledge Base article: https://www.syncfusion.com/kb/11254/how-to-disable-some-items-winforms-combobox-dropdown
+
+## Screenshot
+![Disable items in ComboBox](SfComboBox/SfComboBox/ComboBox%20Images/Disable%20some%20items%20in%20ComboBox.png)