Solved

C# Single line if Statement return Null

Posted on 2007-11-24
19
729 Views
Last Modified: 2013-12-16
I have C# enum. If selected value is Customer(ie value 0) i want to return NULL in a Single line If Statement.
I am getting syntax Errors
 
public enum tables
  {
   customer
   Orders
   OrderDetail
}


public int GetTable(tables tableEnum)
     {
       int iTable = (int)tableEnum;  -- iTable returns 0,1 or 2 as per ENUM
     
            iTable= (iTable == 0) ? int? iTable= null  : iTable;    ---- Synatx Errors
0
Comment
Question by:dotnet0824
  • 7
  • 7
  • 2
  • +2
19 Comments
 
LVL 10

Expert Comment

by:joex911
Comment Utility
Hi, should be:
iTable = (iTable == 0)?null:iTable;

Open in new window

0
 

Author Comment

by:dotnet0824
Comment Utility
Hi,
I tried that I get Error "There is no implicit conversion between Null and Int"... Looks like we have to convert Int To Null as iTable is int    at ?Null
0
 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
why to convert to int previously to evaluation? enum advantage is precisely the legibility for evaluation.
Also, an integer cannot be null, so you have to use the Nullable type.
Something like:


public int? GetTable(tables tableEnum)

{

    return (tableEnum==tables.Customer) ? null : (int)tableEnum;

}

Open in new window

0
 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
This will need to receive the result of GetTable in a similar variable, like:
int? result = GetTable(........);
if (result.HasValue)
{
    // do something with result.Value
}

But this is not  agood approach, maybe you can solve it by returning -1 instead of null, so you don't have to use the nullable type.
0
 

Author Comment

by:dotnet0824
Comment Utility
Hi Jaime,
Sorry the function return DataType is Dataset . I am v sorry here it is

public DataSet GetTable(tables tableEnum)
     {
       int iTable = (int)tableEnum;  -- iTable returns 0,1 or 2 as per ENUM
     
            iTable= (iTable == 0) ? int? iTable= null  : iTable;    ---- Synatx Errors
0
 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
well, I am more confused now, maybe you need:

public DataSet GetTable(tables tableEnum)
{
    return (tableEnum==tables.Customer) ? null : someCollection[(int)tableEnum];
}

But better send the rest of the code to understand you. I am suspecting you need DataTable as a return value, not DataSet
0
 
LVL 19

Expert Comment

by:SteveH_UK
Comment Utility
The only way you can return NULL is by having a type that supports NULL, which an Enum does not directly.

However, from .NET 2.0, you have access to generics and this lets you have a type that can be Null.  It is called Nullable and is in the System namespace.

Note that you haven't told us anything about where you are getting your DataSet from, and I suspect that this is not what you are actually trying to achieve.
public Nullable(Of DataSet)(tables tableEnum)

{

  return (tableEnum==tables.Customer) ? null : myDataSet;

}

Open in new window

0
 

Author Comment

by:dotnet0824
Comment Utility
its pretty simple James... inCase 0 is passed in Enum I want to pass @iTable value as NULL or else 1 or 2 as per ENUM Thats all i need now ... Only thing i need is if TableENUM value is 0 (ie Customer Passed in) I Want the variable iTable to take Null
public DataSet GetCustomers(tables tableEnum)
     {
       int iTable = (int)tableEnum;  -- iTable returns 0,1 or 2 as per ENUM
           db.AddInParameter(Command, "@Enabled", DbType.Int32, @iTable);
0
 
LVL 29

Expert Comment

by:Göran Andersson
Comment Utility
Here is how you create a value that you can use in a data parameter:

object value = tableEnum==tables.Customer ? DbNull.Value : (int)tableEnum;
0
How to run any project with ease

Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
- Combine task lists, docs, spreadsheets, and chat in one
- View and edit from mobile/offline
- Cut down on emails

 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
@steve,
The nullable type is unnecessary in your example since DataSet is a reference type and can be null.
0
 

Author Comment

by:dotnet0824
Comment Utility
James.. I am trying out what u had given

   tableEnum==tables.Customer ? null : (int)tableEnum;  ===Syntax Error

    I want to pass that NULL value to the following parameter
 db.AddInParameter(Command, "@Enabled", DbType.Int32, PassValueAsVariableFromENUM);
 
0
 
LVL 19

Expert Comment

by:SteveH_UK
Comment Utility
jaime, this is true, my mistake.  I was still thinking in terms of the Enum...
0
 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
As I stated you don't have to convert to int to evaluate, just evaluate at enum level.
With the last code snippet you have posted, the GreenGhost suggestion appear to be well. So, maybe this is what you need:

       object value = tableEnum==tables.Customer ? DbNull.Value : (int)tableEnum;

           db.AddInParameter(Command, "@Enabled", DbType.Int32, value);
0
 

Author Comment

by:dotnet0824
Comment Utility
i tried out this
object value = tableEnum==tables.Customer ? DbNull.Value : (int)tableEnum;
--Error There is no implicit conversion between DbNull and Int
0
 
LVL 55

Expert Comment

by:Jaime Olivares
Comment Utility
better you do:
object value;
if (tableEnum==tables.Customer)
       value = DbNull.Value;
else
       value = (int)tableEnum;
0
 

Author Comment

by:dotnet0824
Comment Utility
cant it be done in a Single Line If Statement..........Can u please check this   Should we use ?int which is nullable int..  
http://www.experts-exchange.com/Programming/Languages/C_Sharp/Q_22157027.html?sfQueryTermInfo=1+convert+int+null
0
 
LVL 55

Accepted Solution

by:
Jaime Olivares earned 200 total points
Comment Utility
it can be as my first suggestion:

int? value = (tableEnum==tables.Customer) ? null : (int?)tableEnum;
0
 
LVL 29

Assisted Solution

by:Göran Andersson
Göran Andersson earned 100 total points
Comment Utility
You just have to cast the values to object:

object value = tableEnum==tables.Customer ? (object)DbNull.Value : (object)(int)tableEnum;
0
 

Author Comment

by:dotnet0824
Comment Utility
Thanks Jaime. I tried out ur last Posting and it worked Great.
Thanks GreenGhost. Converting to object worked too. I have increased points by 100 and assigning
0

Featured Post

Free Trending Threat Insights Every Day

Enhance your security with threat intelligence from the web. Get trending threat insights on hackers, exploits, and suspicious IP addresses delivered to your inbox with our free Cyber Daily.

Join & Write a Comment

Introduction This article shows how to use the open source plupload control to upload multiple images. The images are resized on the client side before uploading and the upload is done in chunks. Background I had to provide a way for user…
Wouldn’t it be nice if you could test whether an element is contained in an array by using a Contains method just like the one available on List objects? Wouldn’t it be good if you could write code like this? (CODE) In .NET 3.5, this is possible…
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.

744 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

14 Experts available now in Live!

Get 1:1 Help Now