有人可以帮助我理解此示例的泛型吗？

Question

public class KI_Payments<TInfo1 ,TInfo2 , TInfo3, TInfo4, TInfo5> : KI_Leaf
{
    TInfo1 A....
    TInfo2 B.....
}

KI_Payments<TInfo1,TInfo2,TInfo3,TInfo4,TInfo5> oPayment = new KI_Payments<TInfo1,TInfo2,TInfo3,TInfo4,TInfo5>();
switch (Something)
{
     case 1:
        oPayment = new KI_Payments<string, string, string,string,string>();
     case 2:
       oPayment = new KI_Payments<string, int, int,int,int>();

}

What I am trying to do is depending on the "Something", i want to declare info1-info5 with different declarations.
Any thoughts? Thanks

Answer 1

Note that generic payments with different type parameters will not be assignment compatible. You cannot do this

KI_Payment<T1,T2,T3,T4,T5> p = 
    new KI_Payment<string,int,int,int,int>(); // Does not compile!

KI_Payment<object,object,object,object,object> p = 
    new KI_Payment<string,int,int,int,int>(); // Does not compile!

Instead, create a base class having only string properties that you can load from and save to the DB.

public abstract class PaymentBase
{
    public string Info1 { get; set; }
    public string Info2 { get; set; }
    public string Info3 { get; set; }
    public string Info4 { get; set; }
    public string Info5 { get; set; }
}

Then create specialized payment types with specialized properties, which are just wrappers for the string properties. These properties convert from and to string if necessary.

public class PaymentTypeX : PaymentBase
{
    public string Name
    {
        get { return Info1; }
        set { Info1 = value; }
    }

    public int Number
    {
        get {
            int n;
            Int32.TryParse(Info2, out n);
            return n; 
        }
        set { Info2 = value.ToString(); }
    }
}

Finally instantiate specific payment types

PaymentBase payment;
switch (Something) { 
    case 1:         
        payment = new PaymentTypeX();
        break;
    case 2:
        payment = new PaymentTypeY();
        break;
} 

Answer 2

Say info1 is a credit card number in one instantiation and a check number in another, are you actually going to treat them exactly the same in the KI_Payments code?

It might be better if you make a class hierarchy with the payment types you need. This way you can better do code reuse if you do need to do special handling of one of these TInfos . Since your table has string columns, this would make it easier for your constructors to take 5 string parameters and interpret them properly. You have not specified what the Something is but you could use something like the Factory pattern to implement the object creation.

On a related topic, having tables with string columns where you actually store other types of data is arguably not a good idea especially if we are talking about databases.