Custom Grouping Order in Grid for Blazor

Environment

Product

Grid for Blazor

Description

I want to group data programmatically in the Telerik Grid for Blazor by one column. The group order must match a specific sequence rather than the default ascending or descending order. I need to sort groups in a custom way, based on a predefined order of the data, or a custom pattern.

This KB article answers the following questions:

• How can I apply custom sorting to groups in the Grid for Blazor?
• What is the approach to sort Grid groups in a non-standard order?
• Can I define a custom sequence for grouped data in the Grid for Blazor?

Solution

To achieve custom grouping order in the Telerik Grid for Blazor, follow these steps:

1. Bind the Grid with the OnRead event to handle data operations manually. Refer to the official documentation for OnRead and Grouping with OnRead

2. Instead of using the ToDataSourceResult() method, group the data with custom code. Each group must be represented by an AggregateFunctionsGroup object. To understand the Grid's expectations, inspect the datasourceResult variable structure and content with a debugger, as shown in Grouping with OnRead.

3. Implement custom sorting logic for grouped data based on your specific order requirements (e.g., D, A, C, B) within the OnRead method.

4. To display multiple property names and values in group headers, consider using the GroupHeaderTemplate.

5. (Optionally) Disable the Grid's Groupable setting to hide the group panel if you want to prevent users from modifying the grouping state.

@using Telerik.Blazor.Components
@using System.Collections.ObjectModel
@using Telerik.DataSource.Extensions
@using Telerik.DataSource

<h1>Custom sort of grouping on a column</h1>

<TelerikGrid OnRead="@ReadTexts"
			 TItem="GridDataModel"
			 OnStateInit="@((GridStateEventArgs<GridDataModel> args) => OnGridStateInit(args))"
			 Groupable="true"
			 Class="my-grid">
	<GridColumns>
		<GridColumn Title="String 1" Field="@nameof(GridDataModel.S1)" />
		<GridColumn Title="String 2" Field="@nameof(GridDataModel.S2)" />
		<GridColumn Title="String 3" Field="@nameof(GridDataModel.S3)" />
		<GridColumn Title="String 4" Field="@nameof(GridDataModel.S4)" />
		<GridColumn Title="String 5" Field="@nameof(GridDataModel.S5)" />
	</GridColumns>
</TelerikGrid>

@code {
	private ObservableCollection<GridDataModel> GridData = new ObservableCollection<GridDataModel>();

	protected override void OnInitialized()
	{
		base.OnInitialized();

		GridData = new ObservableCollection<GridDataModel>
		{
			new(5, "Text D", "Text 5-2", "Text 5-3", "Text 5-4", "Text 5-5"),
			new(1, "Text A", "Text 1-2", "Text 1-3", "Text 1-4", "Text 1-5"),
			new(3, "Text C", "Text 3-2", "Text 3-3", "Text 3-4", "Text 3-5"),
			new(4, "Text C", "Text 4-2", "Text 4-3", "Text 4-4", "Text 4-5"),
			new(2, "Text B", "Text 2-2", "Text 2-3", "Text 2-4", "Text 2-5"),
		};
	}

	protected async Task ReadTexts(GridReadEventArgs args)
	{
		var datasourceResult = GridData.ToDataSourceResult(args.Request);

		// Determine if the data is grouped
		if (args.Request.Groups.Any())
		{
			// Data is grouped, so we need to handle AggregateFunctionsGroup objects
			var groups = datasourceResult.Data.Cast<AggregateFunctionsGroup>().ToList();

			// Custom sort logic for grouped data based on your custom order: D, A, C, B
			List<string> customOrder = new List<string> { "Text D", "Text A", "Text C", "Text B" };
			groups = groups.OrderBy(group => customOrder.IndexOf(group.Key.ToString())).ToList();

			args.Data = groups;
		}
		else
		{
			// Data is not grouped, so we can cast directly to GridDataModel
			var orderedData = datasourceResult.Data.Cast<GridDataModel>()
								.OrderBy(Text => GetCustomOrderIndex(Text.S1))
								.ToList();

			args.Data = orderedData;
		}

		args.Total = datasourceResult.Total;
		args.AggregateResults = datasourceResult.AggregateResults;
	}

	private int GetCustomOrderIndex(string? value)
	{
		// Define the custom order
		List<string> customOrder = new List<string> { "Text D", "Text A", "Text C", "Text B" };

		// Return the index based on the custom order
		return customOrder.IndexOf(value ?? string.Empty);
	}

	protected void OnGridStateInit(GridStateEventArgs<GridDataModel> args)
	{
		GridState<GridDataModel> desiredState = new GridState<GridDataModel>()
		{
			GroupDescriptors = new List<GroupDescriptor>()
			{
				new GroupDescriptor()
				{
					Member = nameof(GridDataModel.S1),
					MemberType = typeof(string),
				}
			}
		};
		args.GridState = desiredState;
	}

	public class GridDataModel
	{
		public int Id { get; init; }
		public string? S1 { get; set; }
		public string? S2 { get; set; }
		public string? S3 { get; set; }
		public string? S4 { get; set; }
		public string? S5 { get; set; }

		public GridDataModel()
		{
			// Editable Telerik components require a parameterless constructor.
		}

		public GridDataModel(
			int id,
			string s1, string s2, string s3, string s4, string s5)
		{
			Id = id;
			S1 = s1;
			S2 = s2;
			S3 = s3;
			S4 = s4;
			S5 = s5;
		}
	}
}

See Also

• OnRead Data Binding
• Manual Operations - Grouping with OnRead
• AggregateFunctionsGroup Class