Question

I am getting this exception…

System.ArgumentNullException: Value cannot be null.
Parameter name: typeName
   at HomeInventory2.Services.Factory.GetService(String servicename) in C:\Users\Protego\Documents\Visual Studio 2010\Projects\HomeInventory2\HomeInventory2\Services\Factory.cs:line 37
   at HomeInventory2.Business.Manager.GetService(String name) in C:\Users\Protego\Documents\Visual Studio 2010\Projects\HomeInventory2\HomeInventory2\Business\Manager.cs:line 14
   at HomeInventory2.Business.InventoryMngr.Create(CreateInventory inv) in C:\Users\Protego\Documents\Visual Studio 2010\Projects\HomeInventory2\HomeInventory2\Business\InventoryMngr.cs:line 19
   at HomeInventory2.Form1.submitButton_Click(Object sender, EventArgs e) in C:\Users\Protego\documents\visual studio 2010\Projects\HomeInventory2\HomeInventory2\Form1.cs:line 52
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

Stemming from this code –

private void submitButton_Click(object sender, EventArgs e)
        {
            CreateInventory create = new CreateInventory();
            create.ItemAmount = textBoxAmount.Text;
            create.ItemCategory = textBoxCategories.Text;
            create.ItemProperties = textBoxValue.Text;
            create.ItemValue = textBoxValue.Text;

            InventoryMngr invtryMngr = new InventoryMngr();
            invtryMngr.Create(create);

        }

That code should end in a file being created with those values being saved to a text file. Obviously something is breaking down along the line – I am assuming in the InventoryMngr file which looks like this.

namespace HomeInventory2.Business
{
    public class InventoryMngr : Manager
    {
        /// <summary>
        /// persists the inventory information
        /// </summary>
        /// <param name="inv"></param>
        public void Create(CreateInventory inv)
        {
            InventorySvc inventorySvc =
            (InventorySvc)GetService(typeof(InventorySvc).Name);
            inventorySvc.CreateInventory(inv);
        }
    }
}

The business manager get service

namespace HomeInventory2.Business
{
    public abstract class Manager
    {
        private Factory factory = Factory.GetInstance();
        protected IService GetService(String name)
        {
            return factory.GetService(name);
        }
    }
}

And the Factory getservice

public IService GetService(string servicename)
{
    Type type;
    Object obj = null;
    try
    {
        type = Type.GetType(GetImplName(servicename));
        obj = Activator.CreateInstance(type);
    }
    catch (Exception e)
    {
        Console.WriteLine("Exception occured: {0}", e);
        throw e;
    }
    return (IService)obj;
}

GetImplName

private string GetImplName(string servicename)
        {
            NameValueCollection settings =
                ConfigurationManager.AppSettings;
            return settings.Get(servicename);
        }

Answer 1

Here’s your problem:

NameValueCollection settings = ConfigurationManager.AppSettings;
return settings.Get(servicename);

Make sure your app.config/web.config has the correct AppSettings values. settings.Get(servicename) isn’t finding a key for servicename.

So if the servicename is “AwesomeService”, you need an element in appSettings like:

<add key="AwesomeService" value="somevalue"/>