38

I am trying to add a [Science.dll] in my project which should be straight forward. But I am getting a problem. Can someone tell me why?

My C# project which I just copied from internet.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.ComponentModel;
using System.Data;
using Science.Mathematics.VectorCalculus;

namespace using_science_dll
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>`enter code here`
    }
}

C:\Csharptutorial\using_science_dll\using_science_dll\Program.cs(7,7): error CS0246: The type or namespace name 'Science' could not be found (are you missing a using directive or an assembly reference?)

Is it because I am using VS 2008?

Science.dll will run in the following frame .Net 4.0 and Visual C# 2010 Express

enter image description here

shA.t
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Shahgee
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    As you can see on the right in your screenshot the reference is broken. So it's natural that the `using` clause won't work. But you need to tell us what the warning/error message on the broken reference is. – CodesInChaos Oct 07 '11 at 10:03
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    You've got a warning in the "References" section of Solution Explorer. What does that warning say? – Jon Skeet Oct 07 '11 at 10:04
  • Visual Studio can't find the Science reference, try to remove and re-add this reference... – 2GDev Oct 07 '11 at 10:06
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    Is Science.dll compiled for .net 4? Judging from the ! in the References Window, it seems that your project is targeting an incompatible .net version. Since you're on VS2008, i assume that the Science.dll is .net 4. Another option is that you target the Client Framework. Right Click your project (using_science_dll) and make sure the Target Framework is not "Client Framework". Don't have VS2008 here so I don't know exactly what it was called. – Michael Stum Oct 07 '11 at 10:06

3 Answers3

46

The DLL must be present at all times - as the name indicates, a reference only tells VS that you're trying to use stuff from the DLL. In the project file, VS stores the actual path and file name of the referenced DLL. If you move or delete it, VS is not able to find it anymore.

I usually create a libs folder within my project's folder where I copy DLLs that are not installed to the GAC. Then, I actually add this folder to my project in VS (show hidden files in VS, then right-click and "Include in project"). I then reference the DLLs from the folder, so when checking into source control, the library is also checked in. This makes it much easier when more than one developer will have to change the project.

(Please make sure to set the build type to "none" and "don't copy to output folder" for the DLL in your project.)

PS: I use a German Visual Studio, so the captions I quoted may not exactly match the English version...

Thorsten Dittmar
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    Hi Thorsten Please tell in more details how to references to DLLs that are inside project/solution. – Paul Verest Oct 15 '11 at 06:31
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    In your project's folder (this is at the level where all your cs files and the csproj file are), create a new folder (name doesn't matter, I usually use "lib"). Copy the DLL to be referenced there. In VS, make sure that you're seeing all files by selecting the project and clicking the button "Show all files". Then press "Refresh", right-click the folder (grayed out) and click "Add to project. Set the build style to "NONE" for the DLL and then, add a reference to the DLL from the new folder. – Thorsten Dittmar Oct 17 '11 at 09:48
11

Have you added the dll into your project references list? If not right click on the project "References" folder and selecet "Add Reference" then use browse to locate your science.dll, select it and click ok.

edit

I can't see the image of your VS instance that some people are referring to and I note that you now say that it works in Net4.0 and VS2010.

VS2008 projects support NET 3.5 by default. I expect that is the problem as your DLL may be NET 4.0 compliant but not NET 3.5.

ChrisBD
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4

In the right hand column under your solution explorer, you can see next to the reference to "Science" its marked as a warning. Either that means it cant find it, or its objecting to it for some other reason. While this is the case and your code requires it (and its not just in the references list) it wont compile.

Please post the warning message, we can try help you further.

BugFinder
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