How to check gridview last row textbox value in asp.net?

Ok great. So what you can do in the button click event you need to get the RowCollection. Try this inside your button click:

string value=null;

foreach (GridViewRow row in YourGridViewName.Rows)
{
var textbox = row.FindControl("YourTextBoxName") as TextBox;
value = textbox.Text;
}


if(!String.IsNotNullOrEmpty(value))
//call your method.


If it satisfies you then please mark the answer as accepted.

Dear,
Y hv 2 use this code, it could be help you.
the code be become on button event 
.

Here is my asp page.
<asp:GridView ID="idgvDetail" runat="server" Width="100%" ShowFooter="true" AutoGenerateColumns="false"
  CssClass="Gridview" HeaderStyle-BackColor="#788801" HeaderStyle-ForeColor="White">
  <AlternatingRowStyle BackColor="#EEEEEE" />
  <Columns>
  <asp:TemplateField HeaderText="Sale ID">
  <ItemTemplate>
  <asp:Label ID="SaleID" runat="server" Text='<%# Eval("SaleID") %>'>asp:Label>
  ItemTemplate>
  asp:TemplateField>
  <asp:BoundField DataField="SaleSrNo" HeaderText="S.No." ItemStyle-Width="10px" />
  <asp:TemplateField HeaderText="Shoes ID">
  <ItemTemplate>
  <asp:Label ID="ShoesID" runat="server" Text='<%# Eval("ShoesID") %>'>asp:Label>
  ItemTemplate>
  asp:TemplateField>
  <asp:TemplateField HeaderText="Shoes Code">
  <ItemTemplate>
  <asp:TextBox ID="ShoesCode" runat="server" Text='<%# Bind("ShoesCode") %>' OnTextChanged="ShoesCode_TextChanged"
  AutoPostBack="true" Width="70px">asp:TextBox>
  ItemTemplate>
  asp:TemplateField>
  <asp:TemplateField HeaderText="Shoes Name">
  <ItemTemplate>
  <asp:Label ID="ShoesName" runat="server" Text='<%# Eval("ShoesName") %>'>asp:Label>
  ItemTemplate>
  asp:TemplateField>
  <asp:TemplateField HeaderText=" Shoes Rate">
  <ItemTemplate>
  <asp:TextBox ID="SaleRate" runat="server" Text='<%# Bind("SaleRate") %>' Width="70px">asp:TextBox>
  ItemTemplate>
  asp:TemplateField>
  <asp:TemplateField HeaderText="Quantity">
  <ItemTemplate>
  <asp:TextBox ID="SaleQty" runat="server" Text='<%# Bind("SaleQty") %>' Width="70px">asp:TextBox>
  ItemTemplate>
   asp:TemplateField>
  <asp:TemplateField HeaderText="Amount">
  <ItemTemplate>
  <asp:Label ID="SaleAmnt" runat="server" Text='<%# Eval("SaleAmnt") %>' Width="70px">asp:Label>
  ItemTemplate>
  <FooterStyle HorizontalAlign="Right" />
  <FooterTemplate>
  <asp:Button ID="btnAddRow" runat="server" CssClass="inputsubmit" Text="Add Row" OnClick="btnAddRow_Click" />
  FooterTemplate>
  asp:TemplateField>
  Columns>
  asp:GridView>
 
---------------------------------------------------------------------
  protected void btnAddRow_Click(object sender, EventArgs e)
  {
//Here I want to check last row data. If the data fill in these textbox (ShoesCode, SaleRate, SaleQty) then AddRowToGrid function work.
           AddRowToGrid();
  }