chore(treelist): add rowcontextmenu documentation

Author: jivanova

components/treelist/events.md

@@ -20,6 +20,7 @@ This article explains the events available in the Telerik TreeList for Blazor. T
 	* [OnModelInit](#onmodelinit)
 	* [OnRowClick](#onrowclick)
 	* [OnRowDoubleClick](#onrowdoubleclick)
+	* [OnRowContextMenu](#onrowcontextmenu)
 	* [OnRowRender](#onrowrender)
 	* [OnRowDrop](#onrowdrop)
 	* [PageChanged](#pagechanged)
@@ -1165,6 +1166,127 @@ The `OnRowDoubleClick` event fires before selection happens.
 }
 ````
 
+### OnRowContextMenu
+
+The `OnRowContextMenu` event fires as a response to the user right clicking action on a row of the TreeList, the context menu keyboard button or long-touch for mobile devices. The event does not fire when clicking on:
+* `TreeListCommandButton`
+* row selection checkbox
+* expand/collapse button
+* row in edit mode
+
+The event handler receives a `TreeListRowClickEventArgs` object. It provides the model of the clicked row in the `Item` field that you can cast to your model type.
+
+@[template](/_contentTemplates/common/event-arguments.md#rowclick-args)
+
+The `OnRowContextMenu` event can be used to integrate a ContextMenu to the row.
+
+@[template](/_contentTemplates/common/general-info.md#rerender-after-event)
+
+````CSHTML
+@* Get the row model from a context menu action (right click/long tap) *@
+
+<TelerikTreeList Data="@Data"
+                 IdField="Id" 
+				 ParentIdField="ParentId"
+                 Pageable="true"
+				 Width="850px"
+				 Height="400px" 
+				 OnRowContextMenu="@OnRowContextMenuHandler">
+    <TreeListColumns>
+        <TreeListColumn Field="Name" Expandable="true" Width="320px" />
+        <TreeListColumn Field="Id" Width="120px" />
+        <TreeListColumn Field="ParentId" Width="120px" />
+        <TreeListColumn Field="EmailAddress" Width="120px" />
+        <TreeListColumn Field="HireDate" Width="220px" />
+    </TreeListColumns>
+</TelerikTreeList>
+
+<br />
+
+@logger
+
+@code {
+    public string logger { get; set; } = String.Empty;
+	
+    private void OnRowContextMenuHandler(TreeListRowClickEventArgs args)
+    {
+        var clickedRow = args.Item as Employee;
+
+        logger = $"OnRowContextMenu event fired from right clicking on {clickedRow.Name}";
+		
+        @[template](/_contentTemplates/common/event-arguments.md#rowclick-args-example)
+    }
+
+    public List<Employee> Data { get; set; }
+
+    protected override async Task OnInitializedAsync()
+    {
+        Data = await GetTreeListData();
+    }
+
+    // sample model
+
+    public class Employee
+    {
+        // denote the parent-child relationship between items
+        public int Id { get; set; }
+        public int? ParentId { get; set; }
+
+        // custom data fields for display
+        public string Name { get; set; }
+        public string EmailAddress { get; set; }
+        public DateTime HireDate { get; set; }
+    }
+
+    // data generation
+
+    async Task<List<Employee>> GetTreeListData()
+    {
+        List<Employee> data = new List<Employee>();
+
+        for (int i = 1; i < 15; i++)
+        {
+            data.Add(new Employee
+            {
+                Id = i,
+                ParentId = null, // indicates a root-level item
+                Name = $"root: {i}",
+                EmailAddress = $"{i}@example.com",
+                HireDate = DateTime.Now.AddYears(-i)
+            }); ;
+
+            for (int j = 1; j < 4; j++)
+            {
+                int currId = i * 100 + j;
+                data.Add(new Employee
+                {
+                    Id = currId,
+                    ParentId = i,
+                    Name = $"first level child {j} of {i}",
+                    EmailAddress = $"{currId}@example.com",
+                    HireDate = DateTime.Now.AddDays(-currId)
+                });
+
+                for (int k = 1; k < 3; k++)
+                {
+                    int nestedId = currId * 1000 + k;
+                    data.Add(new Employee
+                    {
+                        Id = nestedId,
+                        ParentId = currId,
+                        Name = $"second level child {k} of {i} and {currId}",
+                        EmailAddress = $"{nestedId}@example.com",
+                        HireDate = DateTime.Now.AddMinutes(-nestedId)
+                    }); ;
+                }
+            }
+        }
+
+        return await Task.FromResult(data);
+    }
+}
+````
+
 ### OnRowRender
 
 This event fires upon the rendering of the TreeList rows. It receives an argument of type `TreeListRowRenderEventArgs` which exposes the following fields: