Grid Validation
The Telerik UI for Blazor Grid supports built-in validation that is enabled by default. The Grid passes an EditContext as a cascading value to the editable cells. When you use inline or incell editing, if any validation messages are present, the Grid will render them as Validation Tooltips on hover of the edited input.
In this Article:
Disable Validation
To disable the built-in validation, add a <GridValidationSettings> tag to the <GridSettings> and set the Enabled parameter to false.
@* Disable the built-in validation in the Grid *@
@using System.ComponentModel.DataAnnotations @* for the validation attributes *@
<TelerikGrid Data=@MyData EditMode="@GridEditMode.Inline" Pageable="true" Height="500px"
OnUpdate="@UpdateHandler" OnEdit="@EditHandler" OnDelete="@DeleteHandler" OnCreate="@CreateHandler" OnCancel="@CancelHandler">
<GridSettings>
<GridValidationSettings Enabled="false">
</GridValidationSettings>
</GridSettings>
<GridToolBarTemplate>
<GridCommandButton Command="Add" Icon="@SvgIcon.Plus">Add Employee</GridCommandButton>
</GridToolBarTemplate>
<GridColumns>
<GridColumn Field=@nameof(SampleData.ID) Title="ID" Editable="false" />
<GridColumn Field=@nameof(SampleData.Name) Title="Name" />
<GridCommandColumn>
<GridCommandButton Command="Save" Icon="@SvgIcon.Save" ShowInEdit="true">Update</GridCommandButton>
<GridCommandButton Command="Edit" Icon="@SvgIcon.Pencil">Edit</GridCommandButton>
<GridCommandButton Command="Delete" Icon="@SvgIcon.Trash">Delete</GridCommandButton>
<GridCommandButton Command="Cancel" Icon="@SvgIcon.Cancel" ShowInEdit="true">Cancel</GridCommandButton>
</GridCommandColumn>
</GridColumns>
</TelerikGrid>
@code {
void EditHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// prevent opening for edit based on condition
if (item.ID < 3)
{
args.IsCancelled = true;// the general approach for cancelling an event
}
Console.WriteLine("Edit event is fired.");
}
async Task UpdateHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// perform actual data source operations here through your service
await MyService.Update(item);
// update the local view-model data with the service data
await GetGridData();
Console.WriteLine("Update event is fired.");
}
async Task DeleteHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// perform actual data source operation here through your service
await MyService.Delete(item);
// update the local view-model data with the service data
await GetGridData();
Console.WriteLine("Delete event is fired.");
}
async Task CreateHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// perform actual data source operation here through your service
await MyService.Create(item);
// update the local view-model data with the service data
await GetGridData();
Console.WriteLine("Create event is fired.");
}
async Task CancelHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// if necessary, perform actual data source operation here through your service
Console.WriteLine("Cancel event is fired.");
}
// 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; }
[Required]
public string Name { get; set; }
}
public List<SampleData> MyData { get; set; }
async Task GetGridData()
{
MyData = 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 Create(SampleData itemToInsert)
{
itemToInsert.ID = _data.Count + 1;
_data.Insert(0, itemToInsert);
}
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.ToString()
});
}
}
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;
}
}
public static async Task Delete(SampleData itemToDelete)
{
_data.Remove(itemToDelete);
}
}
}
Use a Custom Validator
You can validate the Grid with any validator that uses the EditContext. To change the default validator, add a <ValidatorTemplate> tag in <GridValidationSettings>. Define the custom validator in the ValidatorTemplate.
Such third party tools are not included in the Telerik UI for Blazor package. Your project must reference their NuGet packages explicitly. The code snippet below will not run unless you install an appropriate package first. You can find such in the official FluentValidation documentation.
@using Blazored.FluentValidation
@using FluentValidation
<TelerikGrid Data="@GridData"
Pageable="true"
EditMode="@GridEditMode.Inline"
OnCreate="@CreateHandler"
OnUpdate="@UpdateHandler"
Height="500px">
<GridSettings>
<GridValidationSettings>
<ValidatorTemplate>
<FluentValidationValidator Validator="@Validator" />
</ValidatorTemplate>
</GridValidationSettings>
</GridSettings>
<GridToolBarTemplate>
<GridCommandButton Command="Add" Icon="@SvgIcon.Plus">Add Employee</GridCommandButton>
</GridToolBarTemplate>
<GridColumns>
<GridColumn Field=@nameof(SampleData.ID) Title="ID" Editable="false" Width="80px" />
<GridColumn Field=@nameof(SampleData.Name) Title="Name" />
<GridCommandColumn Width="240px">
<GridCommandButton Command="Edit" Icon="@SvgIcon.Pencil">Edit</GridCommandButton>
<GridCommandButton Command="Save" Icon="@SvgIcon.Save" ShowInEdit="true">Save</GridCommandButton>
<GridCommandButton Command="Cancel" Icon="@SvgIcon.Cancel" ShowInEdit="true">Cancel</GridCommandButton>
</GridCommandColumn>
</GridColumns>
</TelerikGrid>
@code {
private List<SampleData> GridData { get; set; } = new();
private SampleDataValidator Validator = new();
public class SampleDataValidator : AbstractValidator<SampleData>
{
public SampleDataValidator()
{
RuleFor(item => item.Name).NotEmpty().MaximumLength(50);
}
}
private async Task UpdateHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// perform actual data source operations here through your service
await MyService.Update(item);
// update the local view-model data with the service data
await GetGridData();
Console.WriteLine("Update event is fired.");
}
private async Task CreateHandler(GridCommandEventArgs args)
{
SampleData item = (SampleData)args.Item;
// perform actual data source operation here through your service
await MyService.Create(item);
// update the local view-model data with the service data
await GetGridData();
Console.WriteLine("Create event is fired.");
}
private async Task GetGridData()
{
GridData = await MyService.Read();
}
protected override async Task OnInitializedAsync()
{
await GetGridData();
}
public class SampleData
{
public int ID { get; set; }
public string Name { get; set; } = string.Empty;
}
// The following static class mimics an actual data service.
public static class MyService
{
private static List<SampleData> _data { get; set; } = new List<SampleData>();
public static async Task Create(SampleData itemToInsert)
{
itemToInsert.ID = _data.Count + 1;
_data.Insert(0, itemToInsert);
}
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}"
});
}
}
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;
}
}
public static async Task Delete(SampleData itemToDelete)
{
_data.Remove(itemToDelete);
}
}
}
The Telerik components for Blazor do not perform the actual validation of the model. Validation is managed by the
EditContext. The role of the Telerik components is to callEditContextmethods, subscribe toEditContextevents, retrieve validation messages, and display them. If a validation scenario does not work as expected, check the behavior in a standard Blazor<EditForm>to verify if the issue is related to the Telerik components.