C＃遍历类成员以查找特定条件

Question

I have a C# class that gets loaded with a database row (orm)..this object has all the data in it..i need a way to traverse class level members to look for specific condition? the following is the stop-gap I have and There ought to be a better solution.. Is reflection the answer and how? Thanks!

public string findCURRRATEValue()
{
    if (!FUNDNO1.Equals("999") &&
        FUNDTYPE1.Equals("F"))
    {
        return "CURRRATE1" + "#" + CURRRATE1;
    }
    else if (!FUNDNO2.Equals("999") &&
        FUNDTYPE2.Equals("F"))
    {
        return "CURRRATE2" + "#" + CURRRATE2;
    }


------------
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    else if (!FUNDNO59.Equals("999") &&
        FUNDTYPE59.Equals("F"))
    {
        return "CURRRATE59" + "#" + CURRRATE59;
    }
    else if (!FUNDNO60.Equals("999") &&
        FUNDTYPE60.Equals("F"))
    {
        return "CURRRATE60" + "#" + CURRRATE60;
    }
    else
    {
        return "CURRRATEX";
    }
} 

Answer 1

Speaking in reflction terms, this is what you can do:

var type = this.GetType();
var fundNoProperties = type.GetProperties()
    .Where(p => p.Name.StartsWith("FUNDNO"));
foreach (var info in fundNoProperties)
{
    string orderNumber = info.Name.Replace("FUNDNO", "");
    var fundTypeInfo = type.GetProperty("FUNDTYPE" + orderNumber);
    if (info.GetValue(this, null).ToString() == "999" &&
        fundTypeInfo.GetValue(this, null).ToString() == "F")
    {
        var currRate = type.GetProperty("CURRATE" + orderNumber);
        return currRate.Name + currRate.GetValue(this, null).ToString();
    }
}

Of course, I have to agree with people commenting this is not how you design your databases. However, data mining tables might look like this (100+ columns, anyone?) or perhaps old, legacy systems tables (over which we have little control). Dirty tricks are not such terrible solution then.

Answer 2

As others have said it is a problem with the way the database is designed. The best solution would be to create a separate table which holds the current rate for each fund (per @Paulo Santos). However, if you are stuck with this solution (like many of us are), you could use reflection, but reflection is rather slow (see solution by @Achim). You could also put each variable into a Dictionary and access the rate via a Dictionary. This way you don't have to duplicate logic, but if you need to add a field its a matter of adding it to the Dictionary.

Yet another way would be to take the DDD approach and isolate DTOs from entities/value objects. Keep those objects and use them as if they are a DTO rather than a business object. Then create a Fund object with a Rate property and map the DTO object to the business object. Ultimately, this would be the beginning of transitioning to a better data structure-- starting at the C# level.

Answer 3

Yes, you should be able to solve this via Reflection. Pseudocode out of my head which should show the idea, but will probably not compile out of the box:

foreach (PropertyInfo prop in this.GetType().GetProperties())
{
    object val = prop.GetValue(this,new object[0]);
    if (...your condition ...) return "xyz" + value;
}
return "last else case";