How to create two dimensional ArrayList using C# .Net

You cannot add Item like this in ArrayList

arr.add[builderSelectedItem.text , "Builder"];

Add does not accept two arguments.

But you can add like this.

arr.Add(new ListItem(this.ddlBuilders.SelectedItem.Value, "Builder"));

But if you keep this kind of data in ViewState then you will get this error.

Type 'System.Web.UI.WebControls.ListItem' in Assembly 'System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable

So you need to make use of Session for holding ArraList.

Or you can use Dictionary.

In the below code i have shown you how to add ArrayList and Dictionary in Session and ViewState respectively.

HTML

<form id="form1" runat="server">
<div>
    <asp:DropDownList ID="ddlBuilders" runat="server">
        <asp:ListItem Text="Please Select" Value="Please Select" />
        <asp:ListItem Text="Bulider1" Value="Bulider1" />
        <asp:ListItem Text="Bulider2" Value="Bulider2" />
    </asp:DropDownList>
    <br />
    <asp:DropDownList ID="ddlConsultants" runat="server">
        <asp:ListItem Text="Please Select" Value="Please Select" />
        <asp:ListItem Text="Consultant1" Value="Consultant1" />
        <asp:ListItem Text="Consultant2" Value="Consultant2" />
    </asp:DropDownList>
    <asp:Button Text="Save" OnClick="Save" runat="server" />
    <br />
    <asp:Button Text="Bind GridView" OnClick="BindGridView" runat="server" />
    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:BoundField DataField="Text" HeaderText="Text" />
            <asp:BoundField DataField="Value" HeaderText="Value" />
        </Columns>
    </asp:GridView>
    <asp:GridView ID="GridView2" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:BoundField DataField="Key" HeaderText="Key" />
            <asp:BoundField DataField="Value" HeaderText="Value" />
        </Columns>
    </asp:GridView>
</div>
</form>

Namespace

using System.Collections;

C#

protected void Save(object sender, EventArgs e)
{
    ArrayList arr = new ArrayList();
    Dictionary<string, string> dictionay = new Dictionary<string, string>();
    if (this.ddlBuilders.SelectedItem.Value != "Please Select")
    {
        arr.Add(new ListItem(this.ddlBuilders.SelectedItem.Value, "Builder"));
        dictionay.Add(this.ddlBuilders.SelectedItem.Value, "Builder");
    }
    if (this.ddlConsultants.SelectedItem.Value != "Please Select")
    {
        arr.Add(new ListItem(this.ddlConsultants.SelectedItem.Value, "Consultant"));
        dictionay.Add(this.ddlConsultants.SelectedItem.Value, "Consultant");
    }
    Session["SelectedValues"] = arr;
    ViewState["Data"] = dictionay;



}

protected void BindGridView(object sender, EventArgs e)
{
    Dictionary<string, string> dictionay = (Dictionary<string, string>)ViewState["Data"];
    ArrayList arr = (ArrayList)Session["SelectedValues"];
    this.GridView1.DataSource = arr;
    this.GridView1.DataBind();
    this.GridView2.DataSource = dictionay;
    this.GridView2.DataBind();
}