如何在 SaveItem 事件中添加自定义验证消息（最好不要使用数据注释）？它应该显示在“ValidationMessage For=”上下文中。
@using System.ComponentModel.DataAnnotations
@page "/edititem"
<EditForm Model="@model" OnSubmit="@Submit" OnValidSubmit="@SaveItem">
<DataAnnotationsValidator />
<ValidationSummary />
<InputText id="ItemName" @bind-Value="@model.ItemName" />
<ValidationMessage For="@(() => model.ItemName)" />
<button type="submit">Submit</button>
</EditForm>
@code {
ItemModel model = new ItemModel();
private void Submit()
{
}
private void SaveItem()
{
}
public class ItemModel
{
[Required]
public string ItemName{ get; set; }
}
}