dotnet/aspnetcore · error · ArgumentException

The parameter '{nameof(Name)}' for component '{nameof(Cascad

Error message

The parameter '{nameof(Name)}' for component '{nameof(CascadingValue<TValue>)}' does not allow null or empty values.

What it means

Thrown by CascadingValue<TValue>.SetParametersAsync when the Name parameter is explicitly set but resolves to null or an empty string. The Name parameter is optional, but if present it must be a non-empty string so that descendant components can match against it by name. Omitting Name entirely is valid; passing Name="" is not.

Source

Thrown at src/Components/Components/src/CascadingValue.cs:81

        IsFixed = false;

        foreach (var parameter in parameters)
        {
            if (parameter.Name.Equals(nameof(Value), StringComparison.OrdinalIgnoreCase))
            {
                Value = (TValue)parameter.Value;
                hasSuppliedValue = true;
            }
            else if (parameter.Name.Equals(nameof(ChildContent), StringComparison.OrdinalIgnoreCase))
            {
                ChildContent = (RenderFragment)parameter.Value;
            }
            else if (parameter.Name.Equals(nameof(Name), StringComparison.OrdinalIgnoreCase))
            {
                Name = (string)parameter.Value;
                if (string.IsNullOrEmpty(Name))
                {
                    throw new ArgumentException($"The parameter '{nameof(Name)}' for component '{nameof(CascadingValue<TValue>)}' does not allow null or empty values.");
                }
            }
            else if (parameter.Name.Equals(nameof(IsFixed), StringComparison.OrdinalIgnoreCase))
            {
                IsFixed = (bool)parameter.Value;
            }
            else
            {
                throw new ArgumentException($"The component '{nameof(CascadingValue<TValue>)}' does not accept a parameter with the name '{parameter.Name}'.");
            }
        }

        if (_hasSetParametersPreviously && IsFixed != previousFixed)
        {
            throw new InvalidOperationException($"The value of {nameof(IsFixed)} cannot be changed dynamically.");
        }

        _hasSetParametersPreviously = true;

View on GitHub (pinned to 294cab2f9b)

Solutions

1. Remove the Name attribute entirely if you don't need name-based cascading (type-based matching works without it).
2. Ensure the Name value is always a non-empty string when set.
3. Guard the binding: only set Name when the value is non-empty.

Example fix

// before
<CascadingValue Name="@MaybeEmptyName" Value="@_value">
    <Child />
</CascadingValue>

// after
@if (!string.IsNullOrEmpty(MaybeEmptyName))
{
    <CascadingValue Name="@MaybeEmptyName" Value="@_value">
        <Child />
    </CascadingValue>
}
else
{
    <CascadingValue Value="@_value">
        <Child />
    </CascadingValue>
}

if (Name is not null && string.IsNullOrEmpty(Name))
    throw new ArgumentException("CascadingValue Name must be non-empty if set.");

When it happens

Trigger: Writing <CascadingValue Name="" ...> or binding Name to a variable that evaluates to null or empty at render time. The check is at CascadingValue.cs:76-82.

Common situations: Dynamically computing the Name from a variable that is sometimes empty; accidentally leaving Name="" when copy-pasting markup; binding Name to a model field that hasn't been initialized.

Related errors

• Cannot notify about changes because the {GetType()} is confi
• EqualTo validator requires a non-empty "other" parameter.
• FileExtensions validator requires a non-empty "extensions" p
• Range validator requires at least one of "min" or "max" para
• regex validator requires a non-empty "pattern" parameter.

AI-assisted analysis of dotnet/aspnetcore@294cab2f9b (2026-08-06). Data as JSON: /api/errors/d17c1af4f5e980d1. Report an issue: GitHub.