c# - There is no build provider registered for the extension '.dll'

Question

I'm trying to reference to a .dll file from a .aspx web page. However, I get the following error:

Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.

Parser Error Message: There is no build provider registered for the extension '.dll'. You can register one in the <compilation><buildProviders> section in machine.config or web.config. Make sure is has a BuildProviderAppliesToAttribute attribute which includes the value 'Web' or 'All'.

Source Error: 

Line 2:  <%@ Page Title="" Language="C#"   MasterPageFile="CSharpBPTestMaster.master" AutoEventWireup="true" CodeFile="CSharpBPTest.aspx.cs" Inherits="Button"  Debug="true"%>  
Line 3:  
Line 4:  <%@ Register tagprefix="blnc" tagname="Balanced" src="bin/Debug/BalancedTest.dll" %>
Line 5:  
Line 6:

Source File: /preview/1/balanced-csharp-master/src/BalancedTest/CSharpBPTest.aspx    Line: 4 

I'm not sure what I'm doing wrong. I build the .csproj file. I have the following in bin\Debug\:

• Balanced.dll
• Balanced.pdb
• BalancedTest.dll
• BalancedTest.pdb

Here is my CSharpBPTest.aspx:

<%@ Page Title="" Language="C#"   MasterPageFile="CSharpBPTestMaster.master" AutoEventWireup="true" CodeFile="CSharpBPTest.aspx.cs" Inherits="Button"  Debug="true"%>   

<%@ Register tagprefix="blnc" tagname="Balanced" src="bin/Debug/BalancedTest.dll" %>


<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" 
    Runat="Server">
    <form id="form1" runat="server">
    <div>


    <asp:Button ID="button1" runat="server" Text="Submit" OnClick="Button_Command"/>

    <br />


    <br />
            <br><asp:label id="warningLabel" Text="" ForeColor="Red" runat="server"/><br>
    <br />  


    </div>
    </form>
</asp:Content>

And in my C# file, I "import" the project like this (at the top):

using Balanced;

I want to be able to use this compiled .dll file on my C# side. The Balanced.dll is an external library. It just came with the files and a .csproj file. I did a build and now I'm trying to use this Balanced.dll file. Am I missing something? I'm sorry if this is a bad question. I'm new to asp.net and csproj.