CODEWITHSUNDEEP
c#stringconstructor
user1762945
user1762945

Reputation:

C#.NET Can I modify the default construction of strings?

I have seen some posts saying extension constructors don't exist, but I am wondering if there is another way of achieving this.

Essentially, I am tasked with building a series of web services (as message proxies) where potentially full credit card details may be passed into any of the text fields.

The problem I have is that no matter which field somebody puts a full credit card number (on purpose or otherwise), I need to ensure the data is appropriately obfuscated before allowing the data to be used or go anywhere.

Rather than coding a whole raft of explicit calls, and potentially missing fields in the process, I figured it would be great if I could modify the default behaviour of string objects to perform this check whenever they are instantiated. Then there's no chance whatsoever of the data slipping through.

Ignoring the potential performance issues with this approach, is there any way of actually achieving this?

Upvotes: 0

Views: 128

Answers (2)

user1762945
user1762945

Reputation:

In the end, I opted for the approach suggested by @sambomartin

I produced a different class to encapsulate the strings in the properties of my objects.

The real trick was the implicit operator override. Coupled with some of the same interfaces as strings implement, this allowed me to create a class that (so far) operates fairly seemlessly within the code.

public class MyString : IComparable, IComparable<string>, IEnumerable<char>, IEnumerable, IEquatable<string>
{
    #region Static Operators
    public static implicit operator MyString(string value)
    {
        return new MyString(value);
    }

    public static implicit operator string(MyString value)
    {
        return value.value;
    }

    public static bool operator !=(MyString a, MyString b)
    {
        return a.value != b.value;
    }

    public static bool operator ==(MyString a, MyString b)
    {
        return a.value == b.value;
    }

    public static bool operator !=(MyString a, string b)
    {
        return a.value != b;
    }

    public static bool operator ==(MyString a, string b)
    {
        return a.value == b;
    }

    public static bool operator !=(string a, MyString b)
    {
        return a != b.value;
    }

    public static bool operator ==(string a, MyString b)
    {
        return a == b.value;
    }
    #endregion

    private string value;

    public int Length
    {
        get { return (value != null) ? value.Length : 0; }
    }

    public MyString(string value)
    {
        this.value = PciCleaner.Clean(value);
    }

    #region Object Overrides
    public override string ToString()
    {
        return value;
    }

    public override bool Equals(object obj)
    {
        return (value != null) ? value.Equals(obj) : false;
    }

    public override int GetHashCode()
    {
        return (value != null) ? value.GetHashCode() : new object().GetHashCode();
    }
    #endregion

    #region IComparable
    public int CompareTo(object obj)
    {
        return (value != null) ? value.CompareTo(obj) : -1;
    }
    #endregion

    #region IComparable<string>
    public int CompareTo(string other)
    {
        return (value != null) ? value.CompareTo(other) : -1;
    }
    #endregion

    #region IEnumerable<char>
    public IEnumerator<char> GetEnumerator()
    {
        return (value != null) ? value.GetEnumerator() : null;
    }
    #endregion

    #region IEnumerable
    IEnumerator IEnumerable.GetEnumerator()
    {
        return (value != null) ? (value as IEnumerable).GetEnumerator() : null;
    }
    #endregion

    #region IEquatable<string>
    public bool Equals(string other)
    {
        return (value != null) ? value.Equals(other) : false;
    }
    #endregion
}

Upvotes: 0

Moho
Moho

Reputation: 16498

System.Security.SecureString class

http://msdn.microsoft.com/en-us/library/system.security.securestring.aspx

Upvotes: 3

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