[API Proposal]: string.ConstantEmpty

[deeprobin]

Background and motivation

string.Empty is a static readonly empty string. Since this cannot be used in attributes, I would like to suggest that we create a constant version of this.

API Proposal

namespace System
{
    public sealed class String : ICloneable, IComparable, IComparable<string>, IConvertible, IEquatable<string>, System.Collections.Generic.IEnumerable<char>
    {
        // Current:
        public static readonly string Empty = "";

        // Proposal:
        // Naming could also be "ConstEmpty" instead of "ConstantEmpty"
        public const string ConstantEmpty = "";
    }
}

API Usage

[Theory]
[InlineData(string.ConstEmpty)]
// previous: [InlineData("")]
public void MyTest(input) {
    Assert.True(string.IsNullOrEmpty(input));
}

Alternative Designs

No response

Risks

No risks, since only a constant is applied and does not replace the static field.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[stephentoub]

Why not just use ""? Why is a new const better?

[deeprobin]

Why not just use ""? Why is a new const better?

Well I used to prefer string.Empty to "" most of the time (but that does not work in Attributes). Although the static call is not much slower performance-wise.

[teo-tsirpanis]

Although the static call is not much slower performance-wise.

The static call will almost surely be optimized away. Returning "" generates the exact same assembly code as returning string.Empty. Also the IL instructions ldstr "" and ldsfld String.Empty take the same amount of space.

I persume you want to add this constant field to completely avoid writing "" in your code, based on the knowledge that magic strings are a bad practice. But the empty string is not a magic string per se, you could view its two consecutive double quotes as a symbol like || or &&.

[danmoseley]

@deeprobin thanks for the proposal but the consensus seems to be that “” is sufficient and arguably more readable as well.