c# - 为什么 Blazor 假定可空组件参数不为空？

问题描述

我应该如何将可为空的值传递给 Blazor 组件？目前我在构建过程中收到一个错误，抱怨我的值不能为空，但组件参数设置为int?.

组件基础：

public class ProjectNameInputBase : ComponentBase
{
    private string[] _existingProjectNames = new string[0];
    private bool _loaded;

    [Parameter]
    public int? CompanyId { get; set; }

    [Parameter]
    public string ProjectName { get; set; }

    [Parameter]
    public EventCallback<string> ProjectNameChanged { get; set; }

    protected bool Disabled => _loaded;
    protected string[] Errors => 
        _existingProjectNames
            .Where(name => AreNamesEqual(name, ProjectName))
            .Select(name => $"Project with name \"{name}\" already exists in the company")
            .ToArray();

    protected async override Task OnParametersSetAsync()
    {
        if (CompanyId.HasValue)
        {
            _existingProjectNames = await FetchProjectNamesAsync(CompanyId.Value);
            _loaded = true;
        }
    }

    protected async Task HandleProjectNameChanged(ChangeEventArgs e)
    {
        if (ProjectNameChanged.HasDelegate)
        {
            await ProjectNameChanged.InvokeAsync(e.Value as string);
        }
    }

    private static bool AreNamesEqual(string a, string b) => a.Trim().ToLower() == b.Trim().ToLower();

    private async Task<string[]> FetchProjectNamesAsync(int companyId)
    {
        await Task.Delay(500);
        return new[] {
            "Project 1",
            "Project 2",
            "Project 3"
        };
    }
}

零件：

@inherits ProjectNameInputBase

<input type="text" value="@ProjectName" @onchange="@HandleProjectNameChanged" disabled="@Disabled" />
@foreach (var error in Errors)
{
    <small class="error">@error</small>
}

消费组件：

<label>
    Project Name
    <ProjectNameInput CompanyId="@Company?.Id" @bind-ProjectName="@ProjectName" />
</label>

截屏：

标签： c#visual-studiorazorblazor

c# - 为什么 Blazor 假定可空组件参数不为空？

问题描述

解决方案

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