Added new kb article grid-kb-style-filtered-columns

knowledge-base/grid-kb-style-filtered-columns.md

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+---
+title: Change Filtered Columns Color in Grid for Blazor
+description: Learn how to change the background color of filtered columns in the Grid for Blazor for better visibility using CSS.
+type: how-to
+page_title: How to Style Filtered Columns in Telerik Grid for Blazor
+slug: grid-kb-style-filtered-columns
+tags: grid, blazor, styling, filtered columns, css, oncellrender, onstatechanged
+res_type: kb
+ticketid: 1672604
+---
+
+## Environment
+
+<table>
+    <tbody>
+	    <tr>
+	    	<td>Product</td>
+	    	<td>Grid for Blazor</td>
+	    </tr>
+    </tbody>
+</table>
+
+## Description
+
+I want to style filtered columns in the Grid for Blazor using RGBA for better visibility. Specifically, when a filter is applied, I want the background color of column cells to change.
+
+This knowledge base article answers the following questions:
+- How to apply custom styles to filtered columns in a Blazor Grid?
+- How to enhance the visibility of filtered columns in Blazor Grid using CSS?
+
+## Solution
+
+To style filtered columns in a Telerik Grid for Blazor: 
+1. Utilize the [`OnCellRender`]({%slug grid-column-events%}#oncellrender) and [`OnStateChanged`]({%slug grid-state%}#onstatechanged) events 
+2. Apply a custom CSS class to the filtered column when a filter is active
+
+>caption Grid with styled filtered column.
+
+`````CSHTML
+@using Telerik.DataSource.Extensions
+@using Telerik.DataSource
+
+<style>
+    .highlighted-column {
+        background-color: rgba(255, 0, 0, 0.2); /* Change to your desired RGBA */
+        color: #191970;
+    }
+</style>
+
+<TelerikGrid TItem="@Employee" 
+             OnRead="@ReadItems"
+             FilterMode="@GridFilterMode.FilterRow"
+             Sortable="true" 
+             Pageable="true" 
+             OnStateChanged="@OnGridStateChanged">
+    <GridColumns>
+        <GridColumn Field="@nameof(Employee.ID)" Filterable="false" Title="ID" />
+        <GridColumn Field="@nameof(Employee.Name)" OnCellRender="@OnNameColumnCellRender" Title="Name" />
+        <GridColumn Field="@nameof(Employee.HireDate)" OnCellRender="@OnHireDateColumnCellRender" Title="Hire Date" />
+    </GridColumns>
+</TelerikGrid>
+
+@code {
+    private List<Employee> SourceData { get; set; }
+    private string FilteredColumn { get; set; }
+
+    private void OnNameColumnCellRender(GridCellRenderEventArgs args)
+    {
+        if (FilteredColumn == nameof(Employee.Name))
+        {
+            args.Class = "highlighted-column"; // Apply the custom CSS class
+        }
+    }
+
+    private void OnHireDateColumnCellRender(GridCellRenderEventArgs args)
+    {
+        if (FilteredColumn == nameof(Employee.HireDate))
+        {
+            args.Class = "highlighted-column"; // Apply the custom CSS class
+        }
+    }
+
+    private async Task OnGridStateChanged(GridStateEventArgs<Employee> args)
+    {
+        if (args.PropertyName == "FilterDescriptors")
+        {
+            if (args.GridState.FilterDescriptors.Any())
+            {
+                var filterDescriptors = new List<IFilterDescriptor>(args.GridState.FilterDescriptors);
+                var filterDescriptor = filterDescriptors[0] as CompositeFilterDescriptor;
+                var filteredColumn = filterDescriptor.FilterDescriptors[0] as FilterDescriptor;
+
+                // Capture the filtered column's field name
+                FilteredColumn = filteredColumn.Member;
+            }
+            else
+            {
+                FilteredColumn = null; // Reset when no filters are applied
+            }
+
+            StateHasChanged(); // Re-render the grid
+        }
+    }
+
+    protected async Task ReadItems(GridReadEventArgs args)
+    {
+        // Simulate network delay
+        await Task.Delay(100);
+
+        var datasourceResult = SourceData.ToDataSourceResult(args.Request);
+
+        args.Data = datasourceResult.Data;
+        args.Total = datasourceResult.Total;
+    }
+
+    protected override void OnInitialized()
+    {
+        SourceData = GenerateData();
+    }
+
+    private List<Employee> GenerateData()
+    {
+        var result = new List<Employee>();
+        var rand = new Random();
+        for (int i = 0; i < 100; i++)
+        {
+            result.Add(new Employee()
+            {
+                ID = i,
+                Name = "Name " + i,
+                HireDate = DateTime.Now.Date.AddDays(rand.Next(-20, 20))
+            });
+        }
+
+        return result;
+    }
+
+    public class Employee
+    {
+        public int ID { get; set; }
+        public string Name { get; set; }
+        public DateTime HireDate { get; set; }
+    }
+}
+`````
+## See Also
+
+- [Grid Columns](https://docs.telerik.com/blazor-ui/components/grid/columns/bound)
+- [OnCellRender Event](https://docs.telerik.com/blazor-ui/components/grid/columns/events)
+- [OnStateChanged Event](https://docs.telerik.com/blazor-ui/components/grid/state#onstatechanged)
+- [Override the Theme or Apply Custom CSS Styles]({%slug themes-override%})