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My situation is I'm working with a legacy database that has two traits that are common for most of the code - there are many values saved with fixed length that are padded with leading zeros, and also fixed length with trailing white space at the end. Very annoying to deal with, so I'm trying to figure out what the cleanest approach for formatting these values would be.

My main focus right now is on formatting the view models / dtos. I'm just querying the database with Dapper via queries or stored procedures, which get mapped to my DTO class, which gets served as Json through my webapi.

Right now this is what a lot of my model properties end up looking like:

    public string PurchaseOrderNumber
    {
        get => _purchaseOrderNumber.TrimStart('0');
        set => _purchaseOrderNumber = value;
    }

This just ends up being repeated everywhere. It would be nice to be able to do something like this:

[TrimZeros]
public string SupplierName { get; set; }

I could aslo make a function that just does this in SQL, then make this a responsibility of all my sql queries/ stored procedures. This works when I'm using something light like Dapper, but not so much when I'm using Entity Framework.

Any recommendations on how to approach this?

ErpaDerp
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    To get you 5% there, you could write a `TrimZeros()` extension method for `string`. It would be easier to type. – Flydog57 Nov 08 '18 at 00:21
  • You might also look at: https://code.google.com/archive/p/easyprop/ and this (which fiddles with the setter, not the getter, but...): https://stackoverflow.com/questions/4546935/how-to-inject-method-to-auto-property-in-net-framework – Flydog57 Nov 08 '18 at 00:24
  • Also, it might be slightly more efficient to call `TrimStart` in the `set` method (I'm assuming that the PO number doesn't get set more than once, or if it does, it gets set less often than it's read). – Rufus L Nov 08 '18 at 00:58
  • @Flydog57 - I actually have this set up as an extension method just as you said at the moment, just decided to leave that out for clarity since it's what I'm trying to get away from. Still best option I have found though! – ErpaDerp Nov 08 '18 at 06:39

1 Answers1

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You could use implicit casting and a helper class:

public class LegacyString
{
     public string TrimmedValue {get; }

     public LegacyString(string value)
     {
         this.TrimmedValue = value?.TrimStart('0');
     }

     public static implicit operator string(LegacyString legacy)
         => legacy?.TrimmedValue; 

     public static implicit operator LegacyString(string legacyValue)
         => new LegacyString(legacyValue);

     public override string ToString() => this.TrimmedValue;
}

Then all you have to do in your main clasess is 

public LegacyString PurchaseOrderNumber {get;set;}

and you can use it as if it was a string in an assignment

myObj.PurchaseOrderNumber = "00001345";

in an expression to get the value

string poNumber = myObj.PurchaseOrderNumber;

the only thing you'd lose is the ability to declare poNumber as var and expect it to be a string. But even then, if you use poNumber where a string was expected the implict conversion would take care of it for you.

Jens Meinecke
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  • This certainly seems interesting, but at first glance I'm not sure if it will fit my needs, I'm guessing this wouldn't work with EF model binding without special setup in the model builder? Or Dapper or AutoMapper mapping? Or serialize to Json string? I'm going to have to play around with it, I've definitely got use for this setup elsewhere. – ErpaDerp Nov 08 '18 at 06:37