Adding this item as a reference in ASP.net will result in a circular dependency __.net

adding this item as a reference in ASP.net will result in a circular dependency

A reference to "DAL" could not be added. Adding this item as a reference will result in a circular dependency. As shown in the following illustration:

There are several class libraries, the previous reference is not a problem, do the following, the reference error.

Why is this happening, is not I cited too much, there is any way to avoid such a mistake.

Problem Analysis:

A project has two projects in A and B, and B is quoted in a, and a is quoted in B.

Can also be said: A class library Application of Class B library, B class library can no longer reference a class library!!

Issues with circular references

If a reference b,b reference C,c reference A is a circular reference.

Because if C is updated, B will also update, b update, A will also update, then a update, C also want to update. (Dead Circle)

Check the order of the references. It is likely that you have quoted yourself!