dotnet/wpf · error · ArgumentException

SR.DataObject_EmptyFormatNotAllowed

Error message

SR.DataObject_EmptyFormatNotAllowed

What it means

The DataFormat constructor rejects a null or empty name. An empty format name has no meaning in the clipboard/drag-drop format registry, so passing name.Length == 0 throws ArgumentException (SR.DataObject_EmptyFormatNotAllowed).

Solutions

1. Validate the format name is non-empty before constructing DataFormat
2. Throw or log a descriptive error at the input boundary
3. Use DataFormats.GetDataFormat with a registered format name instead of hand-constructing

Example fix

// before
var format = new DataFormat(customName, customId);
// after
if (!string.IsNullOrEmpty(customName))
{
    var format = new DataFormat(customName, customId);
}

if (string.IsNullOrEmpty(name)) throw new ArgumentException("Format name must be non-empty", nameof(name));

static bool IsValidFormatName(string name) => !string.IsNullOrEmpty(name);

try
{
    var format = new DataFormat(name, id);
}
catch (ArgumentException ex)
{
    // name was null or empty; surface a validation error
}

When it happens

Trigger: Calling new DataFormat("", someId) or new DataFormat(name, id) where name is the empty string.

Common situations: Building custom clipboard formats from parsed strings where the parsed token can be empty (e.g. split results); dynamic format names derived from user or registry input.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• InvalidEnumArgumentException(nameof(format), (int)format…
• SR.DataObject_EmptyFormatNotAllowed
• ' ' is not a valid value for ' '.
• ArgumentException(message, name)
• ArgumentNullException(name)

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/8e0c7a723f9ed1a3. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/DataFormat.cs:22

using System.Private.Windows.Ole;

namespace System.Windows;

/// <summary>
///  Represents a data format type.
/// </summary>
public sealed class DataFormat : IDataFormat<DataFormat>
{
    /// <summary>
    ///  Initializes a new instance of the DataFormat class and specifies format name and id.
    /// </summary>
    public DataFormat(string name, int id)
    {
        ArgumentNullException.ThrowIfNull(name);

        if (name.Length == 0)
        {
            throw new ArgumentException(SR.DataObject_EmptyFormatNotAllowed); 
        }

        Name = name;
        Id = id;
    }

    /// <summary>
    ///  Specifies the name of this format.
    /// </summary>
    public string Name { get; }

    /// <summary>
    ///  Specifies the Id number for this format.
    /// </summary>
    public int Id { get; }

    static DataFormat IDataFormat<DataFormat>.Create(string name, int id) => new(name, id);
}

View on GitHub (pinned to 81131a70a4)