No connection string named ‘…’ could be found in the application config file.

Two-tier applications separate the presentation layer and the data layer, and all database access related objects are located in the data-tier.

When the application runs, the config file of the main project is read. In web applications, it is the web.config, in console applications the app.config file.

When you get the following runtime exception

Exception thrown: ‘System.InvalidOperationException’ in EntityFramework.dll
An exception of type ‘System.InvalidOperationException’ occurred in EntityFramework.dll but was not handled in user code
No connection string named ‘…Entities’ could be found in the application config file.

 

  1. Copy the connection string from the app.config file of the data-tier to the main project’s config file.
 <add name="USC_SocialMediaMSSQLEntities" connectionString="metadata=res://*/USC_SocialMedia_MSSQL.csdl|res://*/USC_SocialMedia_MSSQL.ssdl|res://*/USC_SocialMedia_MSSQL.msl;provider=System.Data.SqlClient;provider connection string=&quot;data source=MY_SERVER;initial catalog=MY_DATABASE;user id=MY_USER;password=MY_PASWORD;MultipleActiveResultSets=True;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />

2. This is a sample data access class in the data-layer to read data from the aspNetRoles table.

using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SocialMedia_Data {
	public class SocialMediaData {

		private USC_SocialMediaMSSQLEntities _web;

		public SocialMediaData() {

			// Set up the database connections
			_web = new USC_SocialMediaMSSQLEntities();

		}

		/// Returns the list of Roles
		public List GetRoles() {

			IEnumerable foundRoles = from aspNetRoles in _web.AspNetRoles
						 orderby aspNetRoles.DisplayOrder
						 select aspNetRoles;

			if (null == foundRoles || 0 == foundRoles.Count()) {
				return null;
			}

			return foundRoles.ToList();

		}
	}
}

NotSupportedException: Unable to determine the provider name for provider factory of type ‘MySql.Data.MySqlClient.MySqlClientFactory’. Make sure that the ADO.NET provider is installed or registered in the application config

In a two-tier web application, the data layer is in a separate project. This allows better separation between the presentation layer and the data layer. This way you can reuse the data project in another application that targets the same database.

To access a MySql database you need to add the MySql.Data and MySql.Data.Entity NuGet packages to the data project.

When you develop a two-tier application that targets a MySql database you may get the runtime error

NotSupportedException: Unable to determine the provider name for provider factory of type ‘MySql.Data.MySqlClient.MySqlClientFactory’. Make sure that the ADO.NET provider is installed or registered in the application config.

Even if all database interaction is handled in the data project, and you added the MySql NuGet packages to it, you need to add the MySql.Data and MySql.Data.Entity NuGet packages to the web project too, because the Web.config file contains the connection string that includes the reference to MySql.Data.MySqlClient.

<add name="MY_CONNECTION_NAME" providerName="MySql.Data.MySqlClient" connectionString="server=localhost;port=3306;database=MY_DATABASE;uid=MY_USERNAME;password=MY_PASSWORD" />

At the time of writing do not use version 6.10.6.0 of the packages, it causes the error

Exception thrown: ‘System.TypeLoadException’ in mscorlib.dll
An exception of type ‘System.TypeLoadException’ occurred in mscorlib.dll but was not handled in user code
Inheritance security rules violated by type: ‘MySql.Data.MySqlClient.MySqlProviderServices’. Derived types must either match the security accessibility of the base type or be less accessible.

Until a new, corrected version is published, install version 6.9.11.0 of both packages in both projects.

For more information on how to connect to a MySql database from Visual Studio see Connect to a MySQL database from Visual Studio 2017

 

 

The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)

When I made changes to the web.config file of an ASP.Net C# application, I have accidentally deleted a comma, and I started to get the runtime error message:

The given assembly name or codebase was invalid. (Exception from HRESULT: 0x80131047)

Make sure all necessary commas are there in the config files, Visual Studio does not check the format of those lines. In my case, the error was in

<provider invariantName="MySql.Data.MySqlClient" type="MySql.Data.MySqlClient.MySqlProviderServices, MySql.Data.Entity.EF6, Version=6.9.10.0, Culture=neutral, PublicKeyToken=c5687fc88969c44d" />

The .NET MVC model has to have a parameterless constructor

When you create a class to be used as the model in a .NET MVC application, the class has to have a parameterless constructor. It is called during the POST when the user clicks the submit button of the form. If the class does not have a parameterless constructor, we will get the following generic error message. None of the breakpoints can help you to find the cause, and there is no entry in the event log.

The website cannot display the page
HTTP 500

Most likely causes:
•The website is under maintenance.
•The website has a programming error.

What you can try:
Refresh the page.
Go back to the previous page.
More information

No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer

When you move your Visual Studio solution to another workstation you may encounter the following error message:

System.Data.Entity.Core.MappingException was unhandled by user code
HResult=-2146232032
Message=Schema specified is not valid. Errors:
: error 2062: No mapping specified for instances of the EntitySet and AssociationSet in the EntityContainer …
Source=EntityFramework

 

In this case it may help if you re-import the database objects into the .edmx file.

To import all objects again:

  • Open the .edmx file,
  • Press the Ctrl-A keys to select all tables in the diagram,
  • Press the delete key on the keyboard to delete all tables,
  • Right click the white area and select Model Browser,
  • In the Model Browser expand the {model name}.Store, and the Stored Procedures / Functions element
  • Delete all functions and stored procedures
  • In the {model name} element (the element above the {model name}.Store) expand the Function Imports element
  • Delete all function imports
  • Save the .edmx file
  • Right click the white area of the .edmx file and select Update Model from Database
  • Select all necessary tables, stored procedures, and functions and import them.

If you re-import the tables, but do not delete the stored procedures, functions, and function imports you may get the following error message:

HResult=-2146233079
Message=The function import ‘Tobacco_WebEntities.spGetAgeGroupId’ cannot be executed because it is not mapped to a store function.
Source=EntityFramework

 

Save the key file password in Visual Studio

When you have already set up the project signing of the C# application for ClickOnce deployment, and move the solution to another workstation you may get the following error message when you build the solution:

Severity Code Description Project File Line Suppression State
Error Cannot import the following key file: .....pfx. The key file may be password protected. To correct this, try to import the certificate again or manually install the certificate to the Strong Name CSP with the following key container name: VS_KEY_....

We get this message, because the new workstation does not know the key file password. To solve this problem, we have to save the key file password on the new workstation.

To make your solution work again

  • Open the Visual Studio project properties window,
  • On the Signing tab click the pull down that shows the name of the key file.
  • Select Browse,
  • Select the key file,
  • Enter the password in the Password text box.

There is already an open DataReader associated with this Command which must be closed first

When your MVC 5 web application page tries to read the database using the Entity Framework in a loop you may get the following error message:

InnerException: System.InvalidOperationException
HResult=-2146233079
Message=There is already an open DataReader associated with this Command which must be closed first.
Source=System.Data

This usually happens when a cshtml page receives an IEnumerable<> model from the database and makes repeated calls to retrieve the rows one-by-one in a foreach loop.

If your page does not display paged data, read the rows into a List  with the ToList() method and send the list to the cshtml page to iterate through it. This forces the application to read all appropriate rows with one call from the database.

Sometimes you can also eliminate the problem if you add the following to the connection string in the web.config file:

;multipleactiveresultsets=True

Windows web service authentication in IIS Express

When you develop a SOAP web service in Visual Studio 2013 the IDE uses IIS Express for testing. To set up Windows authentication in IIS Express follow the steps below:

Create a Local Security Group on your computer

  • Right click Computer and select Manage
  • On the left side expand Local Users and Groups
  • Right click the Groups folder and select New Group
  • Create a group with the name WebserviceUsers for the users of the web service
  • Right click the Users folder and select New User
  • Create a user and add it to the WebserviceUsers security group

Add the following lines to the  <system.web> section of the Web.config file of your web service application

<authentication mode=”Windows”/>
<authorization>
<allow roles=”WebserviceUsers”/>
<deny users=”*”/>
</authorization>

Set up IIS Express for Windows authentication

  • Select the web service project in the Solution Explorer
  • In the View menu select Properties Window
  • Disable Anonymous Authentication and enable Windows Authentication
    Visual Studio IIS Express Windows Authentication Properties Window

 

In the caller application call the web service with user name and password

  • Add the following lines to your class to supply the credentials
private Webservice.Service _Webservice = new Service();

// Constructor
public Business() {
    string webserviceUrl = "Webservice_Url";
    string webserviceUserName = "Webservice_UserName";
    string webservicePassword = "Webservice_Password";
    _Webservice.Url = webserviceUrl;
    ICredentials credentials = new NetworkCredential(webserviceUserName, webservicePassword);
    _Webservice.Credentials = credentials;
}

How to add tooltip to a Windows Form

In Windows Form applications the tooltip functionality is not built into the controls as in HTML objects.

To add tooltip to your controls on Windows Forms

  • Open the Windows Form in the designer
  • Drag the ToolTip control from the Common Controls section of the Toolbox to the form. The ToolTip control will be placed at the bottom margin of the design surface outside of the visible area of the form.
  • A new item appears in the Misc section of the property list of the form controls (buttons, textboxes, etc): ToolTip on toolTip1
  • Enter the text there you want the users to see when they hover above the control.

How to add a DataGridView to a Windows Form

To display data in a DataGridView on a Windows Form

  • Add a new form to the Win Form Application project
  • Drag a BindingSource from the Toolbox to the form
    Visual Studio Toolbox Data

 

  • The bindingSource object appears below the form
    Visual Studio DataGridview Binding DatSource insert

 

  • Rename the Binding Source
    • Select the bindingSource1 object below the form
    • Press F4 to display the Properties
    • Change the Name property to reflect the purpose of the object
      Visual Studio DataGridview Binding DatSource properties

 

  • Select the DataSource item in the Data section and click the Add Project Data Source… link
    Visual Studio DataGridview Binding DatSource properties select data source

The name is misleading. At this step we are not selecting the source of the data, we are selecting the object that describes the data row. The DataGridView will generate the columns based on the object we will select here.

  • To load the data from a class select Object as the Data Source Type and click Next
    Visual Studio DataGridview Binding Data Source properties choose data source type

 

  • Select the object that describes the data row you want to display
    Visual Studio DataGridview Binding Data Source properties select data object

 

  • Drag a DataGridView from the Toolbox to the form
    Visual Studio Toolbox Data data grid view

 

  • Select the small arrow at the upper right corner of the DataGridView to open the Tasks dialog
  • Click the down arrow next tot the Choose Data Source list
  • Select the Binding Data Source that you added to the form
    Visual Studio DataGridview select binding data source

 

  • Click the Edit Columns link to set the visibility of the columns
    Visual Studio DataGridview Edit Columns

 

  • To hide a column set the Visible attribute in the Appearance section to False
    Visual Studio DataGridview Column visibility
  • To load data into the DatGridView add the following code to the constructor of the form. In this example the GetUsers() method returns an array of UserView objects
    // Load the data into the DataGridView
    bindingSourceUsers.DataSource = _business.GetUsers();
  • To hide the row selector column on the left side of the data add the following to the constructor of the form. This option is not included in the property sheet of the DataGridView, so we have to set it in the code.
    dataGridView1.RowHeadersVisible = false;