Question

in one of my projects I’m using following two methods. 1. GetDoubleValue and 2. GetIntValue. GetDoubleValue uses double.TryParse to parameter str string and returns 0 if it fails while GetIntValue tries int.TryParse to parameter str string and returns 0 if it fails. What I want is to combine these two methods into one generic method that alongwith string str receives parameter T as well so that if I want to use GetDoubleValue Method I can use double for the parameter T and if I want to use GetIntValue Method I can use Int for the parameter T

public double GetDoubleValue(string str)
{
    double d;
    double.TryParse(str, out d);
    return d;
}
public int GetIntValue(string str)
{
    int i;
    int.TryParse(str, out i);
    return i;
}

Note: I have tried something like this;

private T GetDoubleOrIntValue<T>(string str) where T : struct 
{
    T t;
    t.TryParse(str, out t);
    return t;
}

EDIT

In my database I have more than 30 columns in differenct tables having numeric datatype. I want to insert 0 in each column if user does not type anything in the textbox i.e he leaves all or some of the textboxes empty. If I don’t use the GetIntValue method I will have to use the method body more than 30 times. that is why I am doing this through method approach. I’m writing three of more than thirty examples for instance

cmd.Parameters.Add("@AddmissionFee", SqlDbType.Decimal).Value = GetIntValue(tbadmissionfee.Text);
cmd.Parameters.Add("@ComputerFee", SqlDbType.Decimal).Value = GetIntValue(tbcomputerfee.Text);
cmd.Parameters.Add("@NotesCharges", SqlDbType.Decimal).Value = GetDoubleValue(tbnotescharges.Text);

I want to combine the aforesaid two methods because today I’m having two methods like this which if combined will not give any better improvement in the programming but tomorrow I may have tens of methods like this that will better be combined into one generic method. e.g I may have GetInt32Value, GetShortValue etc. hope it is now cleared why I want this???

Answer 1

You could do something like this:

   public static T GetDoubleOrIntValue<T>(this string str) where T : IConvertible
{
    var thisType = default(T);
    var typeCode = thisType.GetTypeCode();
    if (typeCode == TypeCode.Double)
    {
        double d;
        double.TryParse(str, out d);
        return (T)Convert.ChangeType(d,typeCode) ;
    }
    else if (typeCode == TypeCode.Int32)
    {
        int i;
        int.TryParse(str, out i);
        return (T)Convert.ChangeType(i, typeCode);
    }
    return thisType;
}

Then when you call it:

string d = "1.1";
string i = "3";

double doubleValue = d.GetDoubleOrIntValue<double>();
int intValue = i.GetDoubleOrIntValue<int>();

But the whole thing seems kinda silly to me.

EDIT: Saw someone else using Convert.ChangeType…which provides for a generic return type.