Grid Command Column
The command column of a grid allows you to initiate inline or popup editing, or to execute your own commands.
To define it, add a GridCommandColumn in the GridColumns collection of a grid. The command column takes a collection of GridCommandButton instances that invoke the commands. It also provides the data item context and a Title property to set its header text.
In this article:
Features
The section describes the available features and their use.
The GridCommandButton Tag
The GridCommandButton tag offers the following features:
-
Command- the command that will be invoked. Can be one of the built-in commands (see below), or a custom command name. -
Icon- the command button icon, which can be a font icon, an SVG icon or a custom icon. Use in the same way as the Button componentIcon. -
OnClick- the event handler that the button will fire. If used on a built-in command, this handler will fire before the corresponding CRUD event. Cancelling it will prevent the built-in CRUD event from firing. -
ShowInEdit- a boolean property indicating whether the button is only visible while the user is editing/inserting data. -
ChildContent- the text the button will render. You can also place it between the command button's opening and closing tags. - You can customize the appearance of the
GridCommandButtonby applying the appearance attributes available for the TelerikButton.
Built-in Commands
There are four built-in commands:
-
Add- initiates the creation of a new item. -
Edit- initiates the inline or popup editing (depending on the GridEditMode configuration of the grid). -
Delete- initiates the deletion of an existing item. You can also enable a delete confirmation dialog. -
Save- performs the actual update operation after the data has been changed. Triggers theOnUpdateorOnCreateevent so you can perform the data source operation. Which event is triggered depends on whether the item was created or edited. -
Cancel- aborts the current operation (edit or insert).
The
AddandEditcommands require enabled editing.
The OnClick handler
The OnClick handler of the commands receives an argument of type GridCommandEventArgs that exposes the following properties:
-
IsCancelled- set this to true to prevent the operation if the business logic requires it. -
Item- the model item of the Grid row. You can use it to access the model fields and preform the actual data source operations. This property is applicable only for command buttons that are inside a Grid row, not the toolbar. -
IsNew- a boolean field indicating whether the item was just added through the grid interface.
For handling CRUD operations we recommend that you use the grid events (
OnEdit,OnUpdate,OnCancel,OnCreate). TheOnClickhandler is available for the built-in commands to provide consistency of the API.
Context
The command column provides access to the data item via context. This may be useful for conditional statements or passing parameters to custom business logic.
Use a named context variable to avoid errors when nesting components or RenderFragments in general. In such cases, the exception will be similar to "Child content element ... uses the same parameter name ('context') as enclosing child content element ...".
Using GridCommandColumn context
<GridCommandColumn Context="dataItem">
@{
var product = dataItem as ProductModel;
if (product.Discontinued)
{
<GridCommandButton Command="Delete" Icon="@SvgIcon.Trash">Delete</GridCommandButton>
}
else
{
<span>Cannot delete active products</span>
}
}
</GridCommandColumn>
Example
The following code example demonstrates declarations and handling.
The event handlers use
EventCallbackand can be synchronous or async. This example shows async versions, and the signature for the synchronous handlers isvoid MyHandlerName(GridCommandEventArgs args).
Example of handling custom commands in a grid column
@* This sample showcases custom command handling for:
- the built-in Save command that prevents it based on some condition (Name contains "3")
- a custom command for a row
*@
@CustomCommandResult
<TelerikGrid Data=@GridData EditMode="@GridEditMode.Inline" OnUpdate="@MyOnUpdateHandler"
Pageable="true" PageSize="15" Height="500px">
<GridColumns>
<GridColumn Field=@nameof(SampleData.ID) Editable="false" Title="Employee ID" />
<GridColumn Field=@nameof(SampleData.Name) Title="Employee Name" />
<GridColumn Field=@nameof(SampleData.HireDate) Title="Hire Date" />
<GridCommandColumn>
<GridCommandButton Command="Edit" Icon="@SvgIcon.Pencil">Edit</GridCommandButton>
<GridCommandButton Command="Save" Icon="@SvgIcon.Save" ShowInEdit="true" OnClick="@CustomSaveOnClickHandler">Update</GridCommandButton>
<GridCommandButton Command="Cancel" Icon="@SvgIcon.Cancel" ShowInEdit="true">Cancel</GridCommandButton>
<GridCommandButton Command="MyOwnCommand" Icon="@SvgIcon.InfoCircle" ShowInEdit="false" OnClick="@MyCustomCommandOnClickHandler">My Command</GridCommandButton>
</GridCommandColumn>
</GridColumns>
</TelerikGrid>
@code {
//in a real case, keep the models in dedicated locations, this is just an easy to copy and see example
public class SampleData
{
public int ID { get; set; }
public string Name { get; set; }
public DateTime HireDate { get; set; }
}
List<SampleData> GridData { get; set; }
// sample custom commands handling
private async Task CustomSaveOnClickHandler(GridCommandEventArgs args)
{
SampleData theUpdatedItem = args.Item as SampleData;
// any custom logic
if (theUpdatedItem.Name.Contains("3"))
{
// prevent the operation based on a condition. Will prevent the OnUpdate event from firing
CustomCommandResult = new MarkupString(CustomCommandResult + "<br />Update Click fired. Custom logic prevent it from continuing.");
args.IsCancelled = true;
}
}
MarkupString CustomCommandResult;
private async Task MyCustomCommandOnClickHandler(GridCommandEventArgs args)
{
CustomCommandResult = new MarkupString(CustomCommandResult + string.Format("<br />Custom command triggered for item {0}", (args.Item as SampleData).ID));
Console.WriteLine("The Custom command fired. Please wait for the long operation to finish");
}
// sample CRUD operations
private async Task MyOnUpdateHandler(GridCommandEventArgs args)
{
SampleData theUpdatedItem = args.Item as SampleData;
// perform actual data source operations here through your service
await MyService.Update(theUpdatedItem);
// update the local view-model data with the service data
await GetGridData();
}
private async Task GetGridData()
{
GridData = await MyService.Read();
}
protected override async Task OnInitializedAsync()
{
await GetGridData();
}
// the following static class mimics an actual data service that handles the actual data source
// replace it with your actual service through the DI, this only mimics how the API can look like and works for this standalone page
public static class MyService
{
private static List<SampleData> _data { get; set; } = new List<SampleData>();
public static async Task<List<SampleData>> Read()
{
if (_data.Count < 1)
{
for (int i = 1; i < 50; i++)
{
_data.Add(new SampleData()
{
ID = i,
Name = "name " + i,
HireDate = DateTime.Now.AddDays(-i)
});
}
}
return await Task.FromResult(_data);
}
public static async Task Update(SampleData itemToUpdate)
{
var index = _data.FindIndex(i => i.ID == itemToUpdate.ID);
if (index != -1)
{
_data[index] = itemToUpdate;
}
}
}
}
The result from the code snippet above, after the custom command button was clicked on the first row, and after the user tried to edit the second row to put the number "3" in the Name column.
