c#asp.netgridviewwebformsviewstate
Viewstate list loses data on click row edit in GridView
I am new to using Viewstate in asp Web forms. I have a description drop down menu that I use to show a Gridview.
However, when I click on the edit row button, the Gridview clears all data. From this:
to this:
My code is:
public partial class Default : System.Web.UI.Page
{
private List<PRAssembly> assemblyPR = null;
......
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
SBOConnection.Connect();
if (Request.QueryString["message"] == "success")
AlertSuccess.Visible = true;
}
}
private void bindPRGridView()
{
// Create Data Table
DataTable dt = new DataTable();
dt.Columns.Add("LineNum", typeof(int));
dt.Columns.Add("ItemCode", typeof(string));
dt.Columns.Add("ItemDescription", typeof(string));
dt.Columns.Add("Quantity", typeof(int));
if (assemblyPR != null)
{
foreach (var item in assemblyPR)
{
dt.Rows.Add(item.LineNum, item.ItemCode, item.ItemDesc, item.Quantity);
}
pRGridView.DataSource = dt;
pRGridView.DataBind();
if (pRGridView.Rows.Count > 0)
{
pRGridView.UseAccessibleHeader = true;
pRGridView.HeaderRow.TableSection = TableRowSection.TableHeader;
}
pRGridView.Columns[4].Visible = true;
}
else
{
dt.Rows.Add(dt.NewRow());
pRGridView.DataSource = dt;
pRGridView.DataBind();
pRGridView.Columns[4].Visible = false;
foreach (GridViewRow row in pRGridView.Rows)
{
if (row.RowType == DataControlRowType.DataRow)
{
LinkButton lb = ((LinkButton)row.FindControl("lnkRemove"));
lb.Visible = false;
}
}
}
}
protected void AddRowPurchaseRequisition(object sender, EventArgs e)
{
string itemCode = ((DropDownList)pRGridView.FooterRow.FindControl("ddlItemCode")).SelectedValue;
string itemDesc = ((DropDownList)pRGridView.FooterRow.FindControl("ddlItemDescription")).SelectedValue;
int quantity = Int32.Parse(((TextBox)pRGridView.FooterRow.FindControl("txtQuantity")).Text);
assemblyPR = ViewState["PRList"] as List<PRAssembly>;
if (assemblyPR == null)
{
assemblyPR = new List<PRAssembly>();
ViewState["PRList"] = assemblyPR;
}
// Transform data to PRAssembly Class object
assemblyPR.Add(new PRAssembly
{
ItemCode = itemCode,
ItemDesc = itemDesc,
Quantity = quantity
});
// Rebind Grid view
bindPRGridView();
}
protected void pRGridView_RowEditing(object sender, GridViewEditEventArgs e)
{
pRGridView.EditIndex = e.NewEditIndex;
bindPRGridView();
}
After the edit button click, I notice that assemblyPR is null when it comes to rebinding the gridview. How do I allow editing without losing the data?
Below is some Gridview markup
<asp:GridView ID="pRGridView"
runat="server"
AutoGenerateColumns="False"
AllowPaging="True"
AllowSorting="True"
ShowFooter="True"
OnRowEditing="pRGridView_RowEditing"
OnRowUpdating="pRGridView_RowUpdating"
OnPageIndexChanging="pRGridView_PageIndexChanging"
OnRowCancelingEdit="pRGridView_RowCancelingEdit"
PagerStyle-CssClass="bs-pagination"
ShowHeaderWhenEmpty="True"
EmptyDataText="No Records Found"
CssClass="table table-striped table-bordered table-hover table-condensed">
<Columns>
<asp:TemplateField ItemStyle-Width="30px" HeaderText="#">
<ItemTemplate>
<%# Container.DataItemIndex + 1 %>
</ItemTemplate>
<%-- <FooterTemplate>
<%# pRGridView.Rows.Count %>
</FooterTemplate>--%>
</asp:TemplateField>
<asp:TemplateField ItemStyle-Width="120px" HeaderText="Item No.">
<ItemTemplate>
<asp:Label ID="lblItemCode" runat="server"
Text='<%# Bind("ItemCode")%>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlItemCode" runat="server"
AutoPostBack="True"
SelectMethod="GetItemCodes"
AppendDataBoundItems="True"
OnSelectedIndexChanged="ddlItemCode_SelectedIndexChanged"
Width="120px"
DataTextField="Value" DataValueField="Key">
<asp:ListItem Value="-1" Text="Select"></asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator runat="server" ControlToValidate="ddlItemCode" Display="Dynamic" ValidationGroup="Edit"
CssClass="text-danger" ErrorMessage="The Item Code field is required." />
</EditItemTemplate>
<FooterTemplate>
<asp:DropDownList ID="ddlItemCode" runat="server"
AutoPostBack="True"
SelectMethod="GetItemCodes"
AppendDataBoundItems="True"
OnSelectedIndexChanged="ddlItemCode_SelectedIndexChanged"
Width="120px"
DataTextField="Value" DataValueField="Key">
<asp:ListItem Value="-1" Text="Select"></asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator runat="server" ControlToValidate="ddlItemCode" Display="Dynamic" ValidationGroup="Insert"
CssClass="text-danger" InitialValue="-1" ErrorMessage="The Item Code field is required." />
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField ItemStyle-Width="400px" HeaderText="Item Description">
<ItemTemplate>
<asp:Label ID="lblItemDescription" runat="server" Width="120px"
Text='<%# Bind("ItemDescription")%>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlItemDescription" runat="server"
AutoPostBack="True"
SelectMethod="GetItemDescriptions"
AppendDataBoundItems="True"
OnSelectedIndexChanged="ddlItemDescription_SelectedIndexChanged"
Width="400px"
DataTextField="Value" DataValueField="Value">
<asp:ListItem Value="-1" Text="Select"></asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator runat="server" ControlToValidate="ddlItemDescription" Display="Dynamic" ValidationGroup="Edit"
CssClass="text-danger" ErrorMessage="The Item Description field is required." />
</EditItemTemplate>
<FooterTemplate>
<asp:DropDownList ID="ddlItemDescription" runat="server"
AutoPostBack="True"
SelectMethod="GetItemDescriptions"
AppendDataBoundItems="True"
OnSelectedIndexChanged="ddlItemDescription_SelectedIndexChanged"
Width="400px"
DataTextField="Value" DataValueField="Value">
<asp:ListItem Value="-1" Text="Select"></asp:ListItem>
</asp:DropDownList>
<asp:RequiredFieldValidator runat="server" ControlToValidate="ddlItemDescription" Display="Dynamic" ValidationGroup="Insert"
CssClass="text-danger" InitialValue="-1" ErrorMessage="The Item Description field is required." />
</FooterTemplate>
</asp:TemplateField>
<asp:TemplateField ItemStyle-Width="120px" HeaderText="Required Qty.">
<ItemTemplate>
<asp:Label ID="lblAmount" runat="server"
Text='<%# Bind("Quantity")%>'></asp:Label>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtQuantity" runat="server" Width="100px"
Text='<%# Bind("Quantity")%>'></asp:TextBox>
<asp:RequiredFieldValidator runat="server" ControlToValidate="txtQuantity" Display="Dynamic" ValidationGroup="Edit"
CssClass="text-danger" ErrorMessage="The Quantity field is required." />
<asp:RegularExpressionValidator ControlToValidate="txtQuantity" runat="server" CssClass="text-danger" Display="Dynamic"
ErrorMessage="Only numbers allowed." ValidationExpression="^[0-9]{0,6}(\.[0-9]{1,2})?$"
ValidationGroup="Edit"></asp:RegularExpressionValidator>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtQuantity" runat="server" Width="100px"></asp:TextBox>
<asp:RequiredFieldValidator runat="server" ControlToValidate="txtQuantity" Display="Dynamic" ValidationGroup="Insert"
CssClass="text-danger" ErrorMessage="The Quantity field is required." />
<asp:RegularExpressionValidator ControlToValidate="txtQuantity" runat="server" CssClass="text-danger" Display="Dynamic"
ErrorMessage="Only numbers allowed." ValidationExpression="^[0-9]{0,6}(\.[0-9]{1,2})?$"
ValidationGroup="Insert"></asp:RegularExpressionValidator>
</FooterTemplate>
</asp:TemplateField>
<asp:CommandField ShowEditButton="True" ValidationGroup="Edit" />
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="lnkRemove" runat="server"
CommandArgument='<%# Bind("LineNum")%>'
OnClientClick="return confirm('Are you sure you want to delete this row?')"
Text="Delete" OnClick="DeleteRowPurchaseRequisition"></asp:LinkButton>
</ItemTemplate>
<FooterTemplate>
<asp:Button ID="btnAdd" runat="server" Text="Add" ValidationGroup="Insert" CssClass="btn btn-primary btn-sm"
OnClick="AddRowPurchaseRequisition" />
</FooterTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="pRGridView" />
</Triggers>
Solution
Upon editing, assemblyPR is null because you're not assigning a value to it prior to calling bindPRGridView(). One way to fix it is by adding a line to pRGridView_RowEditing:
protected void pRGridView_RowEditing(object sender, GridViewEditEventArgs e)
{
pRGridView.EditIndex = e.NewEditIndex;
assemblyPR = ViewState["PRList"] as List<PRAssembly>;
bindPRGridView();
}