How to import file dll of class library into project

In asp.net, before calling class or method from class library in project, you must import dll file (the result of building class library) into the project and add it to references folder. So you can call any classes or methods from the class library to use in your webform. To do this, there are 3 steps:

• Import dll file of class library into project (into bin folder)

• Add the dll file from bin folder into references 

• Import class library namespace wherever you want to call class or method of the class library 

1.  Import dll file of class library into project (into bin folder)  

a. Before import dll file, you must build a class library first. To do this, go to Solution Explorer panel, right click on the class library, and then choose Build. See picture:

Figure 1: Build Class Library

b.  After building Class library, you’ll get a file *.dll (for eg: your class library’s name is ClsLib1, so dll file’s name is ClsLib1.dll). Let’s add it in to bin folder in your project. If  you can’t see bin folder, to be able see bin folder in the project , first click on your project in Solution Explorer panel  and then go to Menu bar--> Click on Project --> choose Show All Files. See picture below :

Figure 2: Show all Files in the project 

c.  Now you can see bin folder and obj folder in the project. So you need to add bin folder in to the project. In Solution Explorer panel, right click on bin folder and then choose Include In Project.

Figure 3:  Include bin folder into the project

 d.  Time to add dll file into bin folder in the project. In Solution Explorer panel, right click on bin folder--> mouse over on Add and then choose Existing Item…. 

Figure 4:  Add dll file into bin folder

e.  When Add Existing Item dialog appear, find your dll file of the class library in your project folder. For example: your file path is C:\Visual Studio 2010\Projects\WebApplication2\ClsLib1\bin\Debug. Your dll file of the class library have the same name as the class library and have extension *.dll. Select the dll file and then click Add button.  See picture:

Figure 5: Select dll file

2.  Add the dll file into references 

 a.  Go to Solution Explorer panel, under the project namespace --> right click on References and then choose Add References. See picture:

Figure 6: Add class library object into references

b. The Add Reference Dialog appear. In Browse Tab, find the dll file of your class library, which you added in bin folder in the project. For example: C:\Visual Studio2010\Projects\WebApplication2\WebApplication2\bin. Select dll file in the bin folder in project and then click OK. See picture below:

Figure 7: Browse dll file add into references

 3.  Import class library namespace wherever you want to call class or method of class library

    a. Import class library namespace

            Syntax: Using Class_Library_Name;

            Example: Your class library namespace is ClsLib1, so code: Using ClsLib1;

   b. Calling class from class library in the project

            Syntax: Class_Name variable_name = new Class_Name();

            Example: Class2 cls2= new Class2(); 

Figure 8: Import namespace of class library and declare class in project

Done ...Now you can calling all classes and methods of class library to use in the project :)