Add Item to DropDownList after delete row from GridView using C# and VB.Net in ASP.Net

Hi akhter,

Check this example. Now please take its reference and correct your code.

HTML

<asp:DropDownList runat="server" ID="ddlitem">
</asp:DropDownList>
<asp:Button Text="Add" runat="server" OnClick="OnAdd" />
<asp:GridView ID="GVSO" runat="server" AutoGenerateColumns="false"
    AutoGenerateDeleteButton="true" OnRowDeleting="GVSO_RowDeleting">
    <Columns>
        <asp:BoundField DataField="Item_Code" HeaderText="Code" />
        <asp:BoundField DataField="Descriptionitem" HeaderText="Description" />
        <asp:BoundField DataField="QTY" HeaderText="Quantity" />
    </Columns>
</asp:GridView>

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[] {
            new DataColumn("Item_Code"),
            new DataColumn("Description")
        });
        dt.Rows.Add(1, "Item 1");
        dt.Rows.Add(2, "Item 2");
        dt.Rows.Add(3, "Item 3");
        dt.Rows.Add(4, "Item 4");
        ViewState["dropdownlistdata"] = dt;
        ddlitem.DataSource = dt;
        ddlitem.DataTextField = "Description";
        ddlitem.DataValueField = "Item_Code";
        ddlitem.DataBind();

        DataTable dt1 = new DataTable();
        dt1.Columns.AddRange(new DataColumn[3] {
            new DataColumn("Item_Code"),
            new DataColumn("Descriptionitem"),
            new DataColumn("QTY")
        });
        dt1.Rows.Add(1, "Item", "10");
        ViewState["dt"] = dt1;
        GVSO.DataSource = dt1;
        GVSO.DataBind();
    }
}

protected void GVSO_RowDeleting(object sender, GridViewDeleteEventArgs e)
{ 
    int index = Convert.ToInt32(e.RowIndex);
    DataTable dt = (DataTable)ViewState["dt"];

    DataTable dtdrop = ViewState["dropdownlistdata"] as DataTable;
    DataRow dr = dtdrop.NewRow();
    dr["Item_Code"] = dt.Rows[index]["Item_Code"];
    dr["Description"] = dt.Rows[index]["Descriptionitem"];
    dtdrop.Rows.Add(dr);
    ViewState["dropdownlistdata"] = dtdrop;

    dt.Rows[index].Delete();
    ViewState["dt"] = dt;
    GVSO.DataSource = dt;
    GVSO.DataBind();        
        
    ddlitem.DataSource = dtdrop;
    ddlitem.DataTextField = "Description";
    ddlitem.DataValueField = "Item_Code";
    ddlitem.DataBind();
}

protected void OnAdd(object sender, EventArgs e)
{
    // get value and text which item you have selected
    int codeitem = Convert.ToInt32(ddlitem.SelectedItem.Value.ToString());
    string Descriptionitem = ddlitem.SelectedItem.Text.ToString();

    //delete the selected item from dropdownlist
    DataTable dtdrop = ViewState["dropdownlistdata"] as DataTable;
    for (int i = dtdrop.Rows.Count - 1; i >= 0; i--)
    {
        DataRow dr1 = dtdrop.Rows[i];
        if (dr1["Item_Code"].ToString() == codeitem.ToString())
            dr1.Delete();
    }
    dtdrop.AcceptChanges();
    ViewState["dropdownlistdata"] = dtdrop;
    ddlitem.DataSource = dtdrop;
    ddlitem.DataTextField = "Description";
    ddlitem.DataValueField = "Item_Code";
    ddlitem.DataBind();

    //add the selected item to gridview
    DataTable dtgridview = ViewState["dt"] as DataTable;
    DataRow dr2 = dtgridview.NewRow();

    dr2["Item_Code"] = codeitem;
    dr2["Descriptionitem"] = Descriptionitem;
    dr2["QTY"] = "5";
    dtgridview.Rows.Add(dr2);
    ViewState["dt"] = dtgridview;
    GVSO.DataSource = dtgridview;
    GVSO.DataBind();
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = New DataTable()
        dt.Columns.AddRange(New DataColumn() {
                            New DataColumn("Item_Code"),
                            New DataColumn("Description")})
        dt.Rows.Add(1, "Item 1")
        dt.Rows.Add(2, "Item 2")
        dt.Rows.Add(3, "Item 3")
        dt.Rows.Add(4, "Item 4")
        ViewState("dropdownlistdata") = dt
        ddlitem.DataSource = dt
        ddlitem.DataTextField = "Description"
        ddlitem.DataValueField = "Item_Code"
        ddlitem.DataBind()
        Dim dt1 As DataTable = New DataTable()
        dt1.Columns.AddRange(New DataColumn(2) {
                                New DataColumn("Item_Code"),
                                New DataColumn("Descriptionitem"),
                                New DataColumn("QTY")})
        dt1.Rows.Add(1, "Item", "10")
        ViewState("dt") = dt1
        GVSO.DataSource = dt1
        GVSO.DataBind()
    End If
End Sub

Protected Sub GVSO_RowDeleting(ByVal sender As Object, ByVal e As GridViewDeleteEventArgs)
    Dim index As Integer = Convert.ToInt32(e.RowIndex)
    Dim dt As DataTable = CType(ViewState("dt"), DataTable)
    Dim dtdrop As DataTable = TryCast(ViewState("dropdownlistdata"), DataTable)
    Dim dr As DataRow = dtdrop.NewRow()
    dr("Item_Code") = dt.Rows(index)("Item_Code")
    dr("Description") = dt.Rows(index)("Descriptionitem")
    dtdrop.Rows.Add(dr)
    ViewState("dropdownlistdata") = dtdrop
    dt.Rows(index).Delete()
    ViewState("dt") = dt
    GVSO.DataSource = dt
    GVSO.DataBind()
    ddlitem.DataSource = dtdrop
    ddlitem.DataTextField = "Description"
    ddlitem.DataValueField = "Item_Code"
    ddlitem.DataBind()
End Sub

Protected Sub OnAdd(ByVal sender As Object, ByVal e As EventArgs)
    Dim codeitem As Integer = Convert.ToInt32(ddlitem.SelectedItem.Value.ToString())
    Dim Descriptionitem As String = ddlitem.SelectedItem.Text.ToString()
    Dim dtdrop As DataTable = TryCast(ViewState("dropdownlistdata"), DataTable)

    For i As Integer = dtdrop.Rows.Count - 1 To 0 Step -1
        Dim dr1 As DataRow = dtdrop.Rows(i)
        If dr1("Item_Code").ToString() = codeitem.ToString() Then dr1.Delete()
    Next

    dtdrop.AcceptChanges()
    ViewState("dropdownlistdata") = dtdrop
    ddlitem.DataSource = dtdrop
    ddlitem.DataTextField = "Description"
    ddlitem.DataValueField = "Item_Code"
    ddlitem.DataBind()
    Dim dtgridview As DataTable = TryCast(ViewState("dt"), DataTable)
    Dim dr2 As DataRow = dtgridview.NewRow()
    dr2("Item_Code") = codeitem
    dr2("Descriptionitem") = Descriptionitem
    dr2("QTY") = "5"
    dtgridview.Rows.Add(dr2)
    ViewState("dt") = dtgridview
    GVSO.DataSource = dtgridview
    GVSO.DataBind()
End Sub

Screenshot