CODEWITHSUNDEEP
c#typesmethodsparameters
Mark Mayo
Mark Mayo

Reputation: 12585

Passing just a type as a parameter in C#

Hypothetically it'd be handy for me to do this:

foo.GetColumnValues(dm.mainColumn, int)
foo.GetColumnValues(dm.mainColumn, string)

where the GetColumns method will call a different method inside depending on the type passed.

Yes, I could do it as a boolean flag or similar, I just wondered if there was a way to perhaps pass this, and then ask:

typeof(arg[1]) or similar...

I could also override the method, use generics, etc - I know there are different ways to do this, I was just curious if this was possible.

Upvotes: 175

Views: 305707

Answers (7)

BorisD
BorisD

Reputation: 1814

Use generic types !

  class DataExtraction<T>
{
    DateRangeReport dateRange;
    List<Predicate> predicates;
    List<string> cids;

    public DataExtraction( DateRangeReport dateRange,
                           List<Predicate> predicates,
                           List<string> cids)            

    {
        this.dateRange = dateRange;
        this.predicates = predicates;
        this.cids = cids;
    }
}

And call it like this :

  DataExtraction<AdPerformanceRow> extractor = new DataExtraction<AdPerformanceRow>(dates, predicates , cids);

Upvotes: 0

Mark Byers
Mark Byers

Reputation: 837906

You can pass a type as an argument, but to do so you must use typeof:

foo.GetColumnValues(dm.mainColumn, typeof(int))

The method would need to accept a parameter with type Type.

where the GetColumns method will call a different method inside depending on the type passed.

If you want this behaviour then you should not pass the type as an argument but instead use a type parameter.

foo.GetColumnValues<int>(dm.mainColumn)

Upvotes: 17

Danny Varod
Danny Varod

Reputation: 18069

foo.GetColumnValues(dm.mainColumn, typeof(int));
foo.GetColumnValues(dm.mainColumn, typeof(string));

Or using generics:

foo.GetColumnValues<int>(dm.mainColumn);
foo.GetColumnValues<string>(dm.mainColumn);

Upvotes: 8

Reed Copsey
Reed Copsey

Reputation: 564323

There are two common approaches. First, you can pass System.Type

object GetColumnValue(string columnName, Type type)
{
    // Here, you can check specific types, as needed:

    if (type == typeof(int)) { // ...

This would be called like: int val = (int)GetColumnValue(columnName, typeof(int));

The other option would be to use generics:

T GetColumnValue<T>(string columnName)
{
    // If you need the type, you can use typeof(T)...

This has the advantage of avoiding the boxing and providing some type safety, and would be called like: int val = GetColumnValue<int>(columnName);

Upvotes: 277

500 - Internal Server Error
500 - Internal Server Error

Reputation: 28829

You can use an argument of type Type - iow, pass typeof(int). You can also use generics for a (probably more efficient) approach.

Upvotes: 0

Kevin DiTraglia
Kevin DiTraglia

Reputation: 26048

You can do this, just wrap it in typeof()

foo.GetColumnValues(typeof(int))

public void GetColumnValues(Type type)
{
    //logic
}

Upvotes: 2

Peter Ritchie
Peter Ritchie

Reputation: 35881

foo.GetColumnValues(dm.mainColumn, typeof(string))

Alternatively, you could use a generic method:

public void GetColumnValues<T>(object mainColumn)
{
    GetColumnValues(mainColumn, typeof(T));
}

and you could then use it like:

foo.GetColumnValues<string>(dm.mainColumn);

Upvotes: 30

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