How do you pass List<T> as argument?

A Repasky

How do you pass List as argument when the T is a class without nameing a class?

Here is what I have:

How do you pass List as argument?

   class ProcessClaims
   {
      public static List<MMORecord> listDataMMO = new List<MMORecord>();
      public static List<PHCSRecord> listDataPHCS = new List<PHCSRecord>();
      public static List<PHCRecord> listDataPHC = new List<PHCRecord>();
      public static List<MMORecord> listDataPHS = new List<MMORecord>();
      public static List<MMORecord> listDataGLB = new List<MMORecord>();
      public static List<PHCRecord> listDataNotcovered = new List<PHCRecord>();
      public static List<MMORecord> listDataDEL = new List<MMORecord>();
      public static List<PHCRecord> listDataMC1 = new List<PHCRecord>();
      public static List<MMORecord> listDataHC = new List<MMORecord>();
      public static List<PHCSRecord> listDataMultiplan = new List<PHCSRecord>(); 



 
The MMORecord, PHCSRecord, PHCRecord are classes.  

 
Then I use it to pass to a Method.

 
      CreateExcelXML.CreateNewSheet(@"E:\MMOExtract\Extract\" + sFilename + Program.extractEndDate + ".xlsx",
         sheet, sheetNum, header, ProcessClaims.listDataPHCS, setNumber);

 
Here is the Method.

 
      public static void CreateNewSheet(string path, string sheetName, UInt32Value sheetNum,
         List<string> header, List<PHCSRecord> listData, List<int> setNumber)

 

How can I pass this List so I do not have to have a Method for each List?  I have 10 List's so I

would have to have 10 Methods.  Then this goes to another Method and I will have to have 10 more Methods.

It will all be duplicate code except for the List which references a class.

 
How can I do this so I can only have one general Method for all 10?  It is passed as a reference, correct?  
 
Thanks for the help ahead of time.  I am still learning C# and .NET.

 
Arep

14 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
It will probably compile if you change that line to:

listData.Add((T)(object)phcsclass);

and work at runtime if you pass the method the appropriate type of list.

However, as the code of the two generic methods stands, they might as well be non-generic because you're creating objects of a specific type, setting their properties and then adding them to the list.
A Repasky14y ago
Vulpes,

That did it and it is all working. I thank you so much. You have been a great help.

Arep
A Repasky14y ago
I am finally getting back. The good news is that I finally got all the OpenXML working. But I have to add more List variables. They I call the 2 Methods with your technique, but there now is an error and I do not know how to fix it.

I get these errors.

Error 2 Argument 1: cannot convert from 'MMOExtract.PHCRecord' to 'T' C:\MMOExtractClass\MMOExtract\MMOExtract\GenExcel.cs 221 23 MMOExtract

Error 4 Argument 1: cannot convert from 'MMOExtract.PHCSRecord' to 'T' C:\MMOExtractClass\MMOExtract\MMOExtract\GenExcel.cs 293 23 MMOExtract

Error 1 The best overloaded method match for 'System.Collections.Generic.List
.Add(T)' has some invalid arguments C:\MMOExtractClass\MMOExtract\MMOExtract\GenExcel.cs 221 10 MMOExtract

Error 3 The best overloaded method match for 'System.Collections.Generic.List.Add(T)' has some invalid arguments C:\MMOExtractClass\MMOExtract\MMOExtract\GenExcel.cs 293 10 MMOExtract

On this:

listData.Add(phcsclass);

What can I do to fix this.

By the way, all of the record classes use IEnumerator. I am using this on another Method and it is working there.

Thanks,

Arep
A Repasky14y ago
They do exactly the same thing. I will try it later. First I wrote individual routines for each class. I have 3 different record classes. First I want to get the multiple sheets on one workbook. Then I will go back and cleanup and try you method of doing this argument passing. I have been busy all day. I really appreciate your help. I will get back.

Arep
Vulpes14y ago
Ah, I can see straightaway that the PHCSRecord implements IEnumerable, so I'd try changing the signature of your generic method to the following:

public static void CreateNewSheet(string path, string sheetName, UInt32Value sheetNum,
List header, List listData, List setNumber) where T : class, IEnumerable
{
// code
}

Even if it now works OK for the PHCSRecord class, it will only work for the other classes if they too implement IEnumerable.
A Repasky14y ago
I cannot get the List> to work. So I would like to continue with your way. I am attaching one of the classes, so you can see how they are created. It was the Lead Programmer that I work with that told me to use the nested List's, and he really pushes to go his way.

So can someone help me? I need to pass the List with a Class to a method,

Thanks for any help.

Arep
A Repasky14y ago
Ok, it did work before with one sheet and I have 2 files that have 3 sheets each. Also, have a total of 10 sheet with others having single sheets. And I have to get it down over the weekend. No, pressure right!

I have to leave now and will work over the weekend. Go to game tonight though.

Arep
Vulpes14y ago
You still won't be able to iterate through the items in the 'classname' object unless it implements IEnumerable or the generic equivalent.

If the code in the nested foreach statement was working before you tried to genericize the method, then PHCSRecord must implement one of these interfaces.
A Repasky14y ago
Someone I work with told me to make a List>. So I am going that way.

Thanks,
Arep
Vulpes14y ago
Can you tell me what interfaces the PHCSRecord and your other classes implement?

To use them generically, they either need to implement some common interfaces or inherit from a common base class.
A Repasky14y ago
When I compiled it I get an error on CreateNewSheet call. The error is:

Error 1 The type 'MMOExtract.PHCSRecord' cannot be used as type parameter 'T' in the generic type or method 'MMOExtract.CreateExcelXML.CreateNewSheet(string, string, DocumentFormat.OpenXml.UInt32Value, System.Collections.Generic.List, System.Collections.Generic.List, System.Collections.Generic.List)'. There is no implicit reference conversion from 'MMOExtract.PHCSRecord' to 'System.Collections.Generic.IEnumerable'.

Thanks, I thought we had it.

Arep
Vulpes14y ago
To use foreach you'll need to specify an additional constraint on T.

The following assumes that your classes implement the generic IEnumerable interface - just replace with IEnumerable if you're implementing the non-generic interface instead:

public static void CreateNewSheet(string path, string sheetName, UInt32Value sheetNum,
List header, List listData, List setNumber) where T : class, IEnumerable
{
// code
}

A Repasky14y ago

Thanks that seemed to compile to pass argument, but I can not test it because I have the following error now. I think it cannot see the items in the class.

Error 1 foreach statement cannot operate on variables of type 'T' because 'T' does not contain a public definition for 'GetEnumerator'

The code at that location is and the problem is at the second foreach statement:

        Row row;
        Cell cell;
        uint rowCnt = 2;
        string cl = "";
        //Loop through the class 
        foreach (var curClass in listData)
          {
            row = new Row();
            int idx = 0;
            foreach (var item in curClass)
            {
               //Set the cell location
               if (idx >= 26)
                  cl = "A" + Convert.ToString(Convert.ToChar(65 + idx - 26));
               else
                  cl = Convert.ToString(Convert.ToChar(65 + idx));
               cell = new Cell();

               
               //ETC.

 
Again, thanks,

 
Arep

Vulpes14y ago
You could 'genericize' your method:

public static void CreateNewSheet(string path, string sheetName, UInt32Value sheetNum,
List header, List<T> listData, List setNumber) where T : class
{
// code
}

You should then be able to call it as before:

CreateExcelXML.CreateNewSheet(@"E:\MMOExtract\Extract\" + sFilename + Program.extractEndDate + ".xlsx",
sheet, sheetNum, header, ProcessClaims.listDataPHCS, setNumber);

The compiler should be able to infer that T is PHCSRecord in this particular call.