SQL: Login failed for user - computername\aspnet - ASP.NET

1.  Open SQL Server Management Studio
2. Create a Database if it is not created already
3. In the root folder of the SQL Server Management Studio there is a -->Security folder-->Expand it
4. In order to create login-->Select Login --> Right click
• Put a login Name
• Select SQL Server authentication if you want
• Uncheck - enforce password policy
• type password
• Select the default database (optional)
• User mapping--> (if you select this option the user name with same login name will be created automatically otherwise you have created manually)
• You can select the database you want to associate & 
• Select the rights 
• dbowner
• datareader
• datawriter
5. Creating create user name manually
• Select the database and expand -->Security-->Users
• Put a user name (it is better to give a same user name as login name)
• Select the login name you just have created
• In the Database role membership select the roles:
• dbowner
• datareader
• datawriter