Question

I’m trying to create a CSV extension method for my enumerable list and I’m stumped. Here’s how I created my simple enumerated list:

var CAquery = from temp in CAtemp
 join casect in CAdb.sectors
 on temp.sector_code equals casect.sector_code
 select new
 {       
     CUSIP = temp.equity_cusip,
     CompName = temp.company_name,
     Exchange = temp.primary_exchange       
 };

CAquery.WriteToCSVFile();

This is what I have done so far in creating an extension method (which I think is wrong):

public static class CSVExtensions
{        
    public static void WriteToCSVFile(this IEnumerable<T> myList)
    {

Do you see what I’m doing wrong?

Answer 1

You have to specify the generic type parameter in the method signature:

public static class CSVExtensions
{        
    public static void WriteToCSVFile<T>(this IEnumerable<T> myList)
    {
       //your code here
    }
}

Are you truly trying to write an extension method that should work on any IEnumerable<T> or is your type more specific? If the later is the case you should replace T with the type you want to support (or add sufficient constraints).

Edit:

In light of comments – you should project to a class instead of an anonymous type in your query – then you can use an extension method for this particular type, i.e.:

class CompanyTicker
{
  public string CUSIP {get;set;}
  public string CompName  {get;set;}
  public string Exchange {get;set;}
}

Now your query can be:

var CAquery = from temp in CAtemp
 join casect in CAdb.sectors
 on temp.sector_code equals casect.sector_code
 select new CompanyTicker
 {       
     CUSIP = temp.equity_cusip,
     CompName = temp.company_name,
     Exchange = temp.primary_exchange       
 };

And your extension method (which now doesn’t need to be generic) becomes:

public static class CSVExtensions
{        
    public static void WriteToCSVFile(this IEnumerable<CompanyTicker> myList)
    {
       //your code here
    }
}