ADO.NET :: Getting Error In Updation Through Gridview

i am trying to update table but geeting error

"System.Data.OleDb.OleDbException: Syntax error in UPDATE statement."

here is my code :

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
string Id = GridView1.DataKeys[e.RowIndex].Values[0].ToString();
TextBox txtDate = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtDate"));
TextBox txtAction = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtAction"));
TextBox txtScrip = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtScrip"));
TextBox txtnBuy = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtnBuy"));
TextBox txtSell = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtSell"));
TextBox txtremarks = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtremarks"));
TextBox txtTarget = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtTarget"));
TextBox txtDifference = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtDifference"));
TextBox txtProfit = ((TextBox)GridView1.Rows[e.RowIndex].FindControl("txtProfit"));
con.Open();
OleDbCommand cmd = new OleDbCommand("UPDATE performance set ndate='" + txtDate.Text + "',Action='" + txtAction.Text
+ "',Scrip='" + txtScrip.Text
+ "',nbuy='" + txtnBuy.Text
+ "',nsell='" + txtSell.Text
+ "',remarks='" + txtremarks.Text
+ "',Target='" + txtTarget.Text
+ "',Difference='" + txtDifference.Text
+ "',nprofit='" + txtProfit.Text
+ "' WHERE nid=" + Id, con);
cmd.ExecuteNonQuery();
con.Close();
GridView1.EditIndex = -1;
bind();
}

<asp:TemplateField HeaderText="Date">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtDate" runat="server" Text='<%#Bind("ndate")%>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%#Eval("ndate") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Action">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtAction" runat="server" Text='<%#Bind("Action")%>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%#Eval("Action") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Scrip">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtScrip" runat="server" Text='<%#Bind("Scrip")%>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%#Eval("Scrip") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Buy Level">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtnBuy" runat="server" Text='<%#Bind("nbuy")%>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label4" runat="server" Text='<%#Eval("nbuy") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Sell Level">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtSell" runat="server" Text='<%#Bind("nsell") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label5" runat="server" Text='<%#Eval("nsell") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Remarks">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtremarks" runat="server" Text='<%#Bind("remarks") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label6" runat="server" Text='<%#Eval("remarks") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Target">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtTarget" runat="server" Text='<%#Bind("Target") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label7" runat="server" Text='<%#Eval("Target") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Difference">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtDifference" runat="server" Text='<%#Bind("Difference") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label10" runat="server" Text='<%#Eval("Difference") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Profit">
<ItemStyle Width="100px" />
<EditItemTemplate>
<asp:TextBox ID="txtProfit" runat="server" Text='<%#Bind("nprofit") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label8" runat="server" Text='<%#Eval("nprofit") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<EditItemTemplate>
<asp:LinkButton ID="link1" runat="server" Text="Update" CommandName="update"></asp:LinkButton>
<asp:LinkButton ID="LinkButton3" runat="server" Text="Cancel" CommandName="cancel"></asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:LinkButton ID="LinkButton4" runat="server" Text="Edit" CommandName="edit"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Delete">
<ItemTemplate>
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False" CommandName="Delete"
Text="Delete"></asp:LinkButton>
<ajaxToolkit:ConfirmButtonExtender ID="ConfirmButtonExtender1" runat="server" ConfirmText="Are You Sure Want to Delete" TargetControlID="LinkButton1">
</ajaxToolkit:ConfirmButtonExtender>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<RowStyle BackColor="#9cd3fa" />
<FooterStyle BackColor="#CCCC99" />
<PagerStyle BackColor="#F7F7DE" ForeColor="Black" HorizontalAlign="Right" />
<SelectedRowStyle BackColor="#CE5D5A" Font-Bold="True" ForeColor="White" />
<HeaderStyle BackColor="#6B696B" Font-Bold="True" ForeColor="White" />
<AlternatingRowStyle BackColor="White" />
</asp:GridView>