Clear the value (selection) of a combobox, dropdown, input
Environment
| Product | ComboBox for Blazor, DropDownList for Blazor, Textbox for Blazor, DatePicker for Blazor, all other inputs and date/time pickers for Blazor |
Description
There is no Clear() method equivalent for combo boxes. How do I clear the selection or value of the input without changing it to the placeholder text value?
Solution
In Blazor, you clear the value of an input (such as a combobox, textbox, doropdownlist, date picker and so on) by changing its Value parameter to the default value for its type (or to a desired other value).
With the MVVM patter used by the framework, you do not need methods like Clear() to remove selection - when the Value matches the default value for its type, the Telerik component will show the placeholder automatically (if one is set).
This approach applies to all inputs
Here are a few examples in their corresponding tabs per component:
Clear an input (or selected item in a dropdown/combobox)
@selectedValue
<br />
<TelerikButton OnClick="@Clear">Clear</TelerikButton>
<TelerikComboBox @bind-Value="selectedValue" Placeholder="Select something"
Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField">
</TelerikComboBox>
@code {
int selectedValue { get; set; }
void Clear()
{
// clear the combo box value (selection)
selectedValue = default;
}
//data binding below
public class MyDdlModel
{
public int MyValueField { get; set; }
public string MyTextField { get; set; }
}
//Define a preselected value when the component initializes
protected override void OnInitialized()
{
selectedValue = 3;
}
IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}
@selectedValue
<br />
<TelerikButton OnClick="@Clear">Clear</TelerikButton>
<TelerikTextBox @bind-Value="@selectedValue" PlaceHolder="type something"></TelerikTextBox>
@code{
string selectedValue { get; set; } = "lorem ipsum";
void Clear()
{
selectedValue = null;
}
}
@selectedValue
<br />
<TelerikButton OnClick="@Clear">Clear</TelerikButton>
<TelerikDropDownList @bind-Value="selectedValue" DefaultText="Select something"
Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField">
</TelerikDropDownList>
@code {
int selectedValue { get; set; }
void Clear()
{
selectedValue = default;
}
//data binding below
public class MyDdlModel
{
public int MyValueField { get; set; }
public string MyTextField { get; set; }
}
//Define a preselected value when the component initializes
protected override void OnInitialized()
{
selectedValue = 3;
}
IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });
}
@selectedValue
<br />
<TelerikButton OnClick="@Clear">Clear</TelerikButton>
<TelerikDatePicker @bind-Value="@selectedValue"></TelerikDatePicker>
@code {
DateTime? selectedValue { get; set; } = DateTime.Now.Date;
void Clear()
{
selectedValue = default;
}
}
@selectedValue
<br />
<TelerikButton OnClick="@Clear">Clear</TelerikButton>
<TelerikNumericTextBox @bind-Value="@selectedValue"></TelerikNumericTextBox>
@code {
int? selectedValue { get; set; } = 123;
void Clear()
{
selectedValue = default;
}
}