list in c# - C# Discussion Boards

1-May-07 1:09

Hello...how can I convert an element from a list into double or integer....I have something like this.......:

totalDemand += Convert.ToDouble(this[j].Demands, CultureInfo.CurrentCulture);

and it gives me an "unable to cast object of type System.Collections.Generic.List'1[system.Double]' to type System.IConvertible'.
and totalDemand it's declared like this:

private double totalDemand;

public double TotalDemand
{
set
{
totalDemand = value;
}
get
{
return totalDemand;
}
}

Stefan Troschuetz1-May-07 1:24

1-May-07 1:24

What kind of value does this[j].Demands return? Convert.ToDouble expects either a string instance or an object that implements the IConvertible interface. According to the error message, this[j].Demands returns neither of them.

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Rick Cook

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lavy28831-May-07 1:29

1-May-07 1:29

this[j].Demands return double....how can I convert it to string or IConvertible?

Stefan Troschuetz1-May-07 1:38

1-May-07 1:38

If this[j].Demands already returns a double, there is no need to "convert" it to a double.

lavy28831-May-07 1:55

1-May-07 1:55

it's about a double and a list of type double...

I wrote something like this :
totalDemand+=this[j].Demands; but it give me two errors....

Error 10 Operator '+=' cannot be applied to operands of type 'double' and 'System.Collections.Generic.List<double>'

Error 11 Cannot implicitly convert type 'System.Collections.Generic.List<double>' to 'double'

Stefan Troschuetz1-May-07 2:07

1-May-07 2:07

Obviously Demands does not return a double but guessing from your comments a list of doubles. Maybe you wanted to write totalDemand += this.Demands[j]? If not, it's probably time to show some more pieces of your code.

lavy28831-May-07 2:20

1-May-07 2:20

Now the problem is that totaldemand is always equal with 0.

The List Demands is making part of the class CityDemand
private List<double> demands = new List<double>();
public List<double> Demands
{
get
{
return demands;
}
set
{
demands = value;
}
}
And this part of the code is in a Class named CitiesDemand

private double totalDemand;

public double TotalDemand
{
set
{
totalDemand = value;
}
get
{
return totalDemand;
}
}
public void CalculateCityDemands(double totalQ)
{
totalDemand = 0;
foreach (CityDemand citydem in this)
{
citydem.Demands.Clear();
for (int i = 0; i <= Count; i++)
{
citydem.Demands.Add(citydem.VehicleQ);

for (int j = 0; j <= i; j++)
{
totalDemand += citydem.Demands[j];
}
}

if (totalDemand > totalQ)
citydem.Demands.RemoveAt(citydem.VehicleQ);
}
}

Christian Graus1-May-07 2:10

Christian Graus

1-May-07 2:10

this[j] runs the indexer on this class. Demands, which it is returning, appears to be a list of doubles. That makes sense, it's name is a plural.

So, totalDemand += this[j].Demands[0]

would work, assuming the list is not empty. Which item in the list do you want to add ?

Convert.ToDouble won't work on a list ( how can it ), and is not needed on a double.

lavy28831-May-07 2:47

1-May-07 2:47

I think the problem is because it'n not adding me something into the list. I dont know exactly, but I have a kind of error like this :
"Index out of range. Must be non-negative and less than the size of collection ".

Christian Graus1-May-07 10:35

Christian Graus

1-May-07 10:35

That means that you're using an array and not a list class. And you're trying to add past the size of the array. Like the error message says.

Class inside namespace

Rick van Woudenberg1-May-07 0:59

Rick van Woudenberg

1-May-07 0:59

Dear all,

This morning I encountered a problem I have never had before. I created a project a few weeks back with the namespace CookBook. It compiles and runs just fine. This morning I opened another project with a different namespace. Compiled it, and this project runs fine too. My sick mind thought it would be nice to combine the two projects, however ... two different namespaces. So I imported the second project in the solution of my first project and changed the namespace of the second project to match the first. After changing the namespace, the entire solution compiles fine. I then wanted to refer to a class inside a form in the second project. Since both projects have the same namespace, you would expect the classes in the second form ( with the changed namespace ) to globally show up as CookBook.[class].

However , this is not the case. It simply tells me : No reference , etc during compilation. Can anyone explain to me , what I am doing wrong. I would like the entire second project to be a part of the first project so I can call classes from inside both forms. The projects are pretty large, so importing the forms ( add existing Item ) into the projects is not an option. Do I have to rebuild the class library somehow ( and if so , how do I do that ? ). I'm using VS2005.

I highly appreciate any input. Kind regards, and many thanks upfront !

Cheers,

PandemoniumPasha1-May-07 1:19

PandemoniumPasha

1-May-07 1:19

i think you have two projects with the same namespace in your solution.
in VS2003, (i don't have VS2005 Frown | :(

this would create two separate .dll library files containing only the functions defined in their respective project files.
so, if you want to use the function from the second project, you will have to import that file and not the first one.

If you want ALL in one file then just combine the two projects together which when compiled will result in a single library file. Roll eyes | :rolleyes:

there may be other methods but i don't know them Blush | :O

i don't know how it works in VS2005, i'm sorry Frown | :(

regards

Stefan Troschuetz1-May-07 1:19

1-May-07 1:19

Having two projects inside the same solution does not make them know anything about each other. In order to use the classes, interfaces, etc. of one project, it has to be referenced by the project that wants to use the stuff. Now that the second project knows about the first one, you can access all things declared public in the first project independent of their namespace.

Rick van Woudenberg1-May-07 1:32

Rick van Woudenberg

1-May-07 1:32

Thank you for your kind and swift reply. I was under the impression that importing a project into a solution automatically meant that they know about each other. Obviously not. However, how can I reference a complete project ( or the namespace for that matter ) into a project.

using CookBook; at the top of the form is still generating the same error during compilation and so is using the complete name ( namespace.class.method ).

Stefan Troschuetz1-May-07 1:41

1-May-07 1:41

Inside the project explorer right-click on "References" and select the "Add reference..." option. In the dialog that opens that should be a "projects" tab.

RSArockiam1-May-07 1:42

RSArockiam

1-May-07 1:42

Try the following way

Rightclick the project->add reference->Project->Select the project

Regards
R.Arockiapathinathan

Rick van Woudenberg1-May-07 2:28

Rick van Woudenberg

1-May-07 2:28

Thank you once again for your reply. But adding project A to B , and B to A would create a circular dependency right ?