Filtering Overview
The ASP.NET Core DropDownList provides options for filtering its data and for displaying only a subset of the data.
Server Filtering
When using Server Filtering a reduced portion of the whole dataset is returned from the server. Displaying a subset of the whole data is useful when working with large datasets, containing thousands of records. In such cases, you can improve performance and loading times by defining a minimum filter length by using the MinLength option. For example, if you set MinLength to 3, the UI for ASP.NET Core DropDownList will not send a request to the remote endpoint and start filtering the dataset until the user enters at least three characters.
When you apply server filtering, only the source of the DropDownList is filtered. To page and filter the dataset, use the virtualization feature.
To configure the UI for ASP.NET Core DropDownList for Server Filtering:
- Set the
ServerFilteringoption of the DataSource component totrue. - Set the
Filterproperty of the DropDownList.
The following example demonstrates how to configure DropDownList for Server Filtering.
@(Html.Kendo().DropDownList()
.Name("products")
.DataTextField("ProductName")
.DataValueField("ProductID")
.Filter(FilterType.Contains)
.DataSource(source =>
{
source.Read(read =>
{
read.Action("ServerFiltering_GetProducts", "DropDownList");
})
.ServerFiltering(true);
})
)
<kendo-dropdownlist name="products"
datatextfield="ProductName"
datavaluefield="ProductID"
filter="FilterType.Contains">
<datasource server-filtering="true">
<transport>
<read url="@Url.Action("ServerFiltering_GetProducts", "DropDownList")" />
</transport>
</datasource>
</kendo-dropdownlist>
public JsonResult ServerFiltering_GetProducts(string text)
{
using (var northwind = GetContext())
{
var products = northwind.Products.Select(product => new ProductViewModel
{
ProductID = product.ProductID,
ProductName = product.ProductName,
UnitPrice = product.UnitPrice.Value,
UnitsInStock = product.UnitsInStock.Value,
UnitsOnOrder = product.UnitsOnOrder.Value,
Discontinued = product.Discontinued
});
if (!string.IsNullOrEmpty(text))
{
products = products.Where(p => p.ProductName.Contains(text));
}
return Json(products.ToList());
}
}
Client Filtering
For smaller sets of data, the UI for ASP.NET Core DropDownList also supports Client Filtering. To configure it, set the ServerFiltering property to false. This way the DropDownList dataset will be filtered on the client without sending additional requests to remote endpoint.
@(Html.Kendo().DropDownList()
.Name("products")
.DataTextField("ProductName")
.DataValueField("ProductID")
.Filter(FilterType.Contains)
.DataSource(source =>
{
source.Read(read =>
{
read.Action("ServerFiltering_GetProducts", "DropDownList");
})
.ServerFiltering(false);
})
)
<kendo-dropdownlist name="products"
datatextfield="ProductName"
datavaluefield="ProductID"
filter="FilterType.Contains">
<datasource server-filtering="false">
<transport>
<read url="@Url.Action("ServerFiltering_GetProducts", "DropDownList")" />
</transport>
</datasource>
</kendo-dropdownlist>
public JsonResult ServerFiltering_GetProducts()
{
using (var northwind = GetContext())
{
var products = northwind.Products.Select(product => new ProductViewModel
{
ProductID = product.ProductID,
ProductName = product.ProductName,
UnitPrice = product.UnitPrice.Value,
UnitsInStock = product.UnitsInStock.Value,
UnitsOnOrder = product.UnitsOnOrder.Value,
Discontinued = product.Discontinued
});
return Json(products.ToList());
}
}