A simple struct that automatically replaces unsupported characters from an Azure Table partition or row key value.

SafeTableKey.cs

/// <summary>
/// A helper class that removes any characters that are unsupported in an Azure Table partition or row key value.
/// </summary>
/// <example>
/// this.PartitionKey = new SafeTableKey("Somestring with unsupported characters");
/// this.RowKey = new SafeTableKey("....");
/// </example>
public struct SafeTableKey : IEquatable<SafeTableKey>
{
    private static readonly ISet<char> reservedCharacters = new HashSet<char> { '\\', '/', '#', '?', '%' };

    public SafeTableKey(string key)
    {
        var builder = new StringBuilder(key);

        for (var i = 0; i < builder.Length; i++)
        {
            if (reservedCharacters.Contains(builder[i]))
            {
                builder[i] = '_';
            }
        }

        this.Key = builder.ToString();
    }

    public string Key { get; }

    public override bool Equals(object? obj)
    {
        return obj is SafeTableKey key &&
               this.Equals(key);
    }

    public override int GetHashCode()
    {
        return HashCode.Combine(this.Key);
    }

    public static implicit operator string(SafeTableKey key)
    {
        return key.Key;
    }

    public bool Equals(SafeTableKey other)
    {
        return this.Key == other.Key;
    }

    public static bool operator ==(SafeTableKey left, SafeTableKey right)
    {
        return left.Equals(right);
    }

    public static bool operator !=(SafeTableKey left, SafeTableKey right)
    {
        return !(left == right);
    }
}