How to bind an Asp.NET details view to an object with a List<string> property

Question

I have the following example entity object

class Entity
{
   public string Name { get; set; }

   public IList<string> Fields { get; set; }
}

Now I have a details view bound to a datagrid and both can display/edit the name property fine, but I want to be able to edit the fields property as well.

I was hoping to use a multi-line textbox to do this. So each line would correspond to an item in the Fields list. But I am having an issue how to bind the list to the textbox so each item is on a new line. I don't think I have an issue of getting the details out and putting them back into the object to save afterwards since I do this manually.

So the question is, Is there a way I can perform a custom bind on the textbox in the details view so each IList item is on a separate line?

Answer 1

Right the answer seems to be as follows:

In the code bind the aspx page create a method as below:

public string CustomBind(object data)
{
   if(data is List<string>)
   {
      List<string> list = data as List<string>;

      return string.Join("\n", list.ToArray();
   }
}

Then in your aspx page you would do the following on the textbox to bind it.

<asp:Textbox TextMode="MultiLine" Text='CustomBind(Eval("MyList"))'></asp:TextBox>

I want to thank Dave for providing this answer in the Newbie ASP.NET Eval question question.

Answer 2

What you are after is something like a nested ListView. Nesting these things gets messy but this should work:

<asp:GridView runat="server" ID="EntityGridView" AutoGenerateColumns="False" 
        EditIndex="0" OnRowUpdating="EntityGridView_RowUpdating">
        <Columns>
            <asp:TemplateField HeaderText="Name">
                <ItemTemplate>
                    <asp:Label ID="NameLabel" runat="server" Text='<%# Bind("Name") %>'></asp:Label>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:TextBox ID="NameTextBox" runat="server" Text='<%# Bind("Name") %>'></asp:TextBox>
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:GridView runat="server" DataSource='<%# Eval("Fields") %>'/>
                </ItemTemplate>
                <EditItemTemplate>
                    <asp:ListView runat="server" DataSource='<%# Eval("Fields") %>' ID="FieldListView">
                        <LayoutTemplate>
                            <asp:PlaceHolder ID="itemPlaceholder" runat="server" />
                        </LayoutTemplate>
                        <ItemTemplate>
                            <asp:TextBox Text='<%# Container.DataItem %>' runat="server" ID="FieldValue"/><br />
                        </ItemTemplate>
                    </asp:ListView>
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:CommandField  ShowEditButton="True" />
        </Columns>
    </asp:GridView>

And your update method will look like:

protected void EntityGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    var updatedEntity = new Entity {Fields = new List<string>()};

    var row = EntityGridView.Rows[e.RowIndex];

    var nameTextBox = (TextBox) row.FindControl("NameTextBox");
    updatedEntity.Name = nameTextBox.Text;

    var fieldListView = (ListView) row.FindControl("FieldListView");
    foreach (var dataItem in fieldListView.Items)
    {
        var fieldValueTextBox = (TextBox)dataItem.FindControl("FieldValue");
        updatedEntity.Fields.Add(fieldValueTextBox.Text);
    }

    // Do your save etc here
}

Then you just bind your list of entities to the GridView.

Answer 3

try something like

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(string[] Fields)
{
// do something with Fields array
}

Answer 4

You can also use the Extension Methods so you don't explicitly have to make the methods for this task on all of your pages.

<asp:TextBox TextMode="MultiLine" ID="txtQuotes" runat="server" Text='<%# ((List<String>) Eval("Quotes")).ToMultiLine() %>' />

 public static class ExtensionMethods
    {      

        public static string ToMultiLine(this List<String> list)
        {
            return String.Join("\n", list.ToArray()); 
        }


    }