I have just tested Telerik sample code from :
https://demos.telerik.com/blazor-ui/dropdownlist/overview
@page "/dropdownlist/overview"
@page "/dropdownlist/index"
@using TelerikBlazorDemos.Shared
<div class="example-box-wrapper">
<div class="example">
<div class="mb-4">T-Shirt size:</div>
<TelerikDropDownList Data="@Data"
@bind-Value=@SelectedSizeMetric
PopupHeight=""
DefaultText="Select your T-shirt size"
ValueField="SizeMetric" TextField="SizeText">
</TelerikDropDownList>
</div>
<div class="ml-4">
Selected Size Number: <strong>@SelectedSizeMetric</strong>
</div>
</div>
@code {
public IEnumerable<Size> Data { get; set; }
public bool AllowCustom { get; set; } = true;
public int? SelectedSizeMetric { get; set; }
public string SelectedSize { get; set; }
public class Size
{
public string SizeText { get; set; }
public int? SizeMetric { get; set; }
}
protected override void OnInitialized()
{
List<Size> sizes = new List<Size>();
sizes.Add(new Size()
{
SizeText = "X-Small",
SizeMetric = 3
});
sizes.Add(new Size()
{
SizeText = "Small",
SizeMetric = 6
});
sizes.Add(new Size()
{
SizeText = "Medium",
SizeMetric = 8
});
sizes.Add(new Size()
{
SizeText = "Large",
SizeMetric = 10
});
sizes.Add(new Size()
{
SizeText = "X-Large",
SizeMetric = 12
});
Data = sizes.AsQueryable();
base.OnInitialized();
}
}
It works fine as it is.
But if I change:
ValueField="SizeMetric" //int type
for:
ValueField="SizeText" //string type
it nolonger works... I get: System.InvalidCastException : 'Unable to cast object of type 'System.String' to type 'System.Nullable`1[System.Int32]'.'
The telerik doc (https://docs.telerik.com/blazor-ui/components/dropdownlist/overview) specifies:
The Value and ValueField can be of types:
number (such as int, double and so on)
string
Guid
Enum