'ItemsControl_SelectionChanged' does not exist in the current context

Question

I am
working through the first example  How To Enable Multiple Row Selection In LightSwitch's
Grids but I get an error with the last line. "_itemsControl.SelectionChanged += newSelectionChangedEventHandler(ItemsControl_SelectionChanged);"

Error 1 The name 'ItemsControl_SelectionChanged' does not exist in the current context C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 48 80 Client

I tried looking up the namespace because it specifically had me adding system.windows.controls to the project even though it already existed in the project by default. I added the using statements above that one because they were generated when I added a code tab for DemoItemList_InitializeDataWorkspace. Other errors were present without those using statements, otherwise my code is the same as the example. I also tried using a prompt visual studio gave me to generate a code stub for the method but that messed things up even more.

My full code is…

using System;

using System.Linq;

using System.IO;

using System.IO.IsolatedStorage;

using System.Collections.Generic;

using Microsoft.LightSwitch;

using Microsoft.LightSwitch.Framework.Client;

using Microsoft.LightSwitch.Presentation;

using Microsoft.LightSwitch.Presentation.Extensions;

//we need this to be able to use DataGrid in our code 

using System.Windows.Controls;

 

namespace LightSwitchApplication

{

    public class DemoItemList

    {

        //although not strictly necessary for this small example 

        //it's good practice to use constants/variables like these 

        //in case you want to use them in more than just the ControlAvailable method 

 

        //this has to match the actual name of the grid control (by default it gets called "grid") 

        private const string ITEMS_CONTROL = "grid";

 

        //this is somewhere to store a reference to the grid control 

        private DataGrid _itemsControl = null;

 

        #region  Event Handlers

        private void DemoItemList_InitializeDataWorkspace(System.Collections.Generic.List<Microsoft.LightSwitch.IDataService> saveChangesTo)

        {

            //here we're adding an event handler to get a reference to the grid control, when it becomes available 

            //and we have no way of knowing when that will be 

            this.FindControl(ITEMS_CONTROL).ControlAvailable += DemoItems_ControlAvailable;

        }

 

        private void DemoItems_ControlAvailable(object send, ControlAvailableEventArgs e)

        {

            //we know that the control is a grid, but we use TryCast, just in case 

            _itemsControl = e.Control as DataGrid;

 

            //if the cast failed, just leave, there's nothing more we can do here 

            if (_itemsControl == null)

            {

                return;

            }

 

            //set the property on the grid that allows multiple selection 

            _itemsControl.SelectionMode = DataGridSelectionMode.Extended;

            _itemsControl.SelectionChanged += new SelectionChangedEventHandler(ItemsControl_SelectionChanged);

        }

        #endregion

 

    }

}

Answer 1

It's not a namespace issue. You just forgot to convert some of the sample code:

        'this is an optional advanced technique, discussed in the bool that Tim Leung & I are currently writing 
        'Pro Visual Studio LightSwitch 2011 Development 
        Private Sub ItemsControl_SelectionChanged() _ 
        Handles _itemsControl.SelectionChanged 
            Select Case (_itemsControl Is Nothing) 
                Case True 
                    _selectedCount = 0 
 
                Case False 
                    _selectedCount = _itemsControl.SelectedItems.Count 
            End Select 
        End Sub 

found in DemoItemList.vb.

Please ask further questions about the sample in the code gallery sample's "Q and A" tab instead of here.

---

Justin Anderson, LightSwitch Development Team

Answer 2

Oh I was at step 4 and using the code from 'listing 1" not converting anything I will try and add this later chunk to see if it changes anything.

I tried adding this code but the same problem exists with "newSelectionChangedEventHandler(ItemsControl_SelectionChanged);"

Error 17 No overload for 'ItemsControl_SelectionChanged' matches delegate 'System.Windows.Controls.SelectionChangedEventHandler' C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 48 47 Client

And now more errors occur...

Error 16 Missing partial modifier on declaration of type 'LightSwitchApplication.DemoItemList'; another partial declaration of this type exists C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 15 18 Client

Error 18 The name '_selectedCount' does not exist in the current context C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 59 21 Client

Error 19 The name '_selectedCount' does not exist in the current context C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 63 21 Client

My code now looks like this

using System;
using System.Linq;
using System.IO;
using System.IO.IsolatedStorage;
using System.Collections.Generic;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Framework.Client;
using Microsoft.LightSwitch.Presentation;
using Microsoft.LightSwitch.Presentation.Extensions;
//we need this to be able to use DataGrid in our code 
using System.Windows.Controls;
 
namespace LightSwitchApplication
{
    public class DemoItemList
    {
        //although not strictly necessary for this small example 
        //it's good practice to use constants/variables like these 
        //in case you want to use them in more than just the ControlAvailable method 
 
        //this has to match the actual name of the grid control (by default it gets called "grid") 
        private const string ITEMS_CONTROL = "grid";
 
        //this is somewhere to store a reference to the grid control 
        private DataGrid _itemsControl = null;
 
        #region  Event Handlers
        private void DemoItemList_InitializeDataWorkspace(List<IDataService> saveChangesTo)
        {
            //here we're adding an event handler to get a reference to the grid control, when it becomes available 
            //and we have no way of knowing when that will be 
            this.FindControl(ITEMS_CONTROL).ControlAvailable += DemoItems_ControlAvailable;
        }
 
        private void DemoItems_ControlAvailable(object send, ControlAvailableEventArgs e)
        {
            //we know that the control is a grid, but we use TryCast, just in case 
            _itemsControl = e.Control as DataGrid;
 
            //if the cast failed, just leave, there's nothing more we can do here 
            if (_itemsControl == null)
            {
                return;
            }
 
            //set the property on the grid that allows multiple selection 
            _itemsControl.SelectionMode = DataGridSelectionMode.Extended;
            _itemsControl.SelectionChanged += new SelectionChangedEventHandler(ItemsControl_SelectionChanged);
        }
 
        //this is an optional advanced technique, discussed in the book 
        //that Tim Leung & I are currently writing 
        //Pro Visual Studio LightSwitch 2011 Development 
        private void ItemsControl_SelectionChanged()
        {
            switch (_itemsControl == null)
            {
                case true:
                    _selectedCount = 0;
                    break;
 
                case false:
                    _selectedCount = _itemsControl.SelectedItems.Count;
                    break;
            }
        } 
        #endregion
 
        partial void ProcessItems_CanExecute(ref bool result)
        {
            // Write your code here.
 
        }
 
    }
}

Answer 3

For error 17:

ItemsControl_SelectionChanged

needs to be changed to

ItemsControl_SelectionChanged(object sender, SelectionChangedEventArgs args)

When I wrote this, I was using VB exclusively. In VB you're able to omit the parameter declarations, but in C# apparently you can't.

For error 18:

Again in VB you don't need to specify the partial keyword for all files, but in C# you do.

For error 19:

It looks like the local variable declaration for _SelectedCount is missing. If you're not using the "advanced" technique, you can comment those lines out. If you are using it, just add

private  _SelectedCount = 0;

underneath

private DataGrid _itemsControl = null;

---

Yann Duran      - Co-Author of Pro Visual Studio LightSwitch 2011      - Author of the  LightSwitch Central Blog FREE Download: Luminous Tools for LightSwitch (a Visual Studio productivity extension for LightSwitch)

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Answer 4

do you mean to replace all of

"new SelectionChangedEventHandler(ItemsControl_SelectionChanged);"

with

"ItemsControl_SelectionChanged(object sender, SelectionChangedEventArgs args); " Because I still receive errors Not sure where to insert this after trying several ways.

Answer 5

No, he wants you to replace:

private void ItemsControl_SelectionChanged()

with:

private void ItemsControl_SelectionChanged(object sender, SelectionChangedEventArgs args)

Just curious, but have you not written event handlers before?

---

Justin Anderson, LightSwitch Development Team

Answer 6

Not in C# only in HTML & ASP.

also what do I have to add to

public class DemoItemList
Error 16 Missing partial modifier on declaration of type 'LightSwitchApplication.DemoItemList'; another partial declaration of this type exists C:\Users\Jordan Walker\Documents\Visual Studio 2012\Projects\AddUrlToNavigationMenu\AddUrlToNavigationMenu\Client\UserCode\DemoItemList.cs 15 18 Client