passing integer array as object array

[Darsin]

Hi all,
I am a new programmer to C# and i am having a following problem.
I want to make a single method which takes a variable length array and
display it contents.
i have defined the method as:

public void DisplayVals(params object [] objArray) {
foreach (object o in objArray)
Console.WriteLine(o.ToString());
}

I am sending it three types of array, one by one:
1. an integer list directly as parameter to the method.
eg. t.DisplayVals(2,4,6,8);
2. an integer array explicitly defined and then sent.
eg. int [] intArray = {1,2,3,4,5,6};
t.DisplayVals(intArray);
3. an user defined type, Employee which has overriden ToString()
method.
eg. Employee [] empArray = new Employee[3];
then created the employee objects with for loop and,
t.DisplayVals(empArray);

In the first and third case the values are shown properly but in the
second case the output is: System.Int32[].
What can i do in the method DisplayVals or with the explicit array
intArray so that the conents of intArray can be displayed. I dont want
to overload DisplayVals method (one for the integers and one for the
user defined types).

The complete code is:

using System;
// A simple class to store in the array
public class Employee {
private int empID;

public Employee (int empID) {
this.empID = empID;
}

public override string ToString() {
return empID.ToString();
}
}

public class Tester {

// // method to take variable number of int parameters and dispaly
them
// public void DisplayVals(params int [] intArray) {
// foreach (int i in intArray)
// Console.WriteLine(i);
// }

// method to take variable number of object parameters and display
them
public void DisplayVals(params object [] objArray) {
foreach (object o in objArray)
Console.WriteLine(o.ToString());
}

public static void Main() {

Tester t = new Tester();

Console.WriteLine("Showing the variable number of integers");
t.DisplayVals(2,3,4,5);

Console.WriteLine("Passing an explicit array");
int [] intArray = {1,2,3,4,5,6};
t.DisplayVals(intArray);

Employee [] empArray = new Employee[3];
// populate the Array
for(int i=0; i<empArray.Length;i++)
empArray = new Employee(i+5);
Console.WriteLine("Passing an Employee Array");
t.DisplayVals(empArray);
}
}

 

[Guest]

The language spec says:

"Array covariance specifically does not extend to arrays of value-types. For
example, no conversion exists that permits an int[] to be treated as an
object[]."

When you pass an int[], it gets loaded into an object[] of length 1 and
passed to your method.

I do not think there is an easy solution - you might be able to do what you
want with reflection.

 

[Ted Miller]

In his specific scenario, he could just do

object[] intArray = { 1,2,3 }

Generics will help with this in 2.0.

 

[Bjorn Abelli]

...

I want to make a single method which takes a variable
length array and display it contents.
i have defined the method as:
[snip]

1. an integer list directly as parameter to the method.
eg. t.DisplayVals(2,4,6,8);
2. an integer array explicitly defined and then sent.
eg. int [] intArray = {1,2,3,4,5,6};
t.DisplayVals(intArray);
3. an user defined type, Employee which has overriden ToString()
method.
eg. Employee [] empArray = new Employee[3];
then created the employee objects with for loop and,
t.DisplayVals(empArray);

This is one possibility:

public void DisplayVals(params object [] objArray)
{
Type at = objArray[0].GetType();

if (at.IsArray)
{
Array a = (Array) objArray[0];

foreach (object o in a)
Console.WriteLine(o.ToString());

}
else
{
foreach (object o in objArray)
Console.WriteLine(o.ToString());
}
}

// Bjorn A

 

[Darsin]

...

I want to make a single method which takes a variable
length array and display it contents.
i have defined the method as:
[snip]

1. an integer list directly as parameter to the method.
eg. t.DisplayVals(2,4,6,8);
2. an integer array explicitly defined and then sent.
eg. int [] intArray = {1,2,3,4,5,6};
t.DisplayVals(intArray);
3. an user defined type, Employee which has overriden ToString()
method.
eg. Employee [] empArray = new Employee[3];
then created the employee objects with for loop and,
t.DisplayVals(empArray);

This is one possibility:

public void DisplayVals(params object [] objArray)
{
Type at = objArray[0].GetType();

if (at.IsArray)
{
Array a = (Array) objArray[0];

foreach (object o in a)
Console.WriteLine(o.ToString());

}
else
{
foreach (object o in objArray)
Console.WriteLine(o.ToString());
}
}

// Bjorn A

thanks for the answer. I was looking for something like this. I could
understand that I have to do some sort of type checking but of what,
that i was not aware due to lack of my knowledge in this matter.
Thanks a lot again.

 

[Darsin]

The language spec says:

"Array covariance specifically does not extend to arrays of value-types. For
example, no conversion exists that permits an int[] to be treated as an
object[]."

When you pass an int[], it gets loaded into an object[] of length 1 and
passed to your method.

I do not think there is an easy solution - you might be able to do what you
want with reflection.

Thanks for the information. I was not aware of this.
Darsin