ComboBox Custom Values

The ComboBox component allows the user to type in their own value that is not a part of the predefined set of options that the developer provided.

The text entered by the user can still go into the field the combo box is bound to through two-way binding.

To enable custom user input set the AllowCustom parameter to true.

When custom values are enabled, the TextField, ValueField and the Value must be of type string. Otherwise an exception will be thrown. Strings are required because the user input can take any form and may not be parsable to other types (such as numbers or GUID).

When custom input is allowed, the ValueChanged event fires on every keystroke, and not when an item is selected, because the ComboBox component acts as a text input.

When custom values are typed in, there may be no selected item in the ComboBox. See the ComboBox Overview - Selected Item article for details on when how item selection and Value work together.

Allow custom user input in the combo box

Selected value: @selectedValue
<br />

<TelerikComboBox Data="@myComboData" TextField="MyTextField" ValueField="MyValueField" @bind-Value="selectedValue"
                 AllowCustom="true"
                 Placeholder="select an item or type your own">
</TelerikComboBox>

@code {
    IEnumerable<MyDdlModel> myComboData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x.ToString() });

    string selectedValue { get; set; } = "lorem ipsum";

    public class MyDdlModel
    {
        public string MyValueField { get; set; } // the ValueField must be a string
        public string MyTextField { get; set; }
    }
}

How to add custom user values into the data source so they are available as items immediately

@*Type a custom value, press enter or click outside. Then, open the combo again and you will see the new custom item in the list*@

@ComboValue
<br />
<TelerikComboBox Data="@Data" @bind-Value="@ComboValue"
                    OnChange="@((object value) => AddItem(value))"
                    TextField="ProductName" ValueField="ProductName"
                    AllowCustom="true" Filterable="true" Placeholder="SELECT A PRODUCT">
</TelerikComboBox>

@code {
    public List<Product> Data { get; set; }
    public string ComboValue { get; set; } = "Product 3";

    protected override void OnInitialized()
    {
        List<Product> products = new List<Product>();
        for (int i = 0; i < 20; i++)
        {
            products.Add(new Product()
            {
                ProductId = i,
                ProductName = $"Product {i}"
            });
        }

        Data = products;

        base.OnInitialized();
    }

    protected void AddItem(object value)
    {
        if (Data.FirstOrDefault(item => item.ProductName == value.ToString()) == null)
        {
            Data.Insert(0, new Product()
            {
                ProductId = Data.Count + 1,
                ProductName = value.ToString()
            });
        }
    }

    public class Product
    {
        // only the Name field is used in the combo, so the Id can be a number
        public int ProductId { get; set; } 
        public string ProductName { get; set; }
    }
}

See Also

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