(ASP.NET) Change TextBoxes attributes (onkeypress) in GridView - asp.net

Question

I have a GridView with Textboxes inside, one for each row.
I need change the attribute "onkeypress" to validate keys.
<asp:Table runat="server">
<asp:TableRow runat="server">
<asp:TableCell runat="server">
<asp:GridView ID="gridview_1" DataSourceID="SqlDataSource3" AutoGenerateColumns="false" runat="server">
<Columns>
<asp:TemplateField HeaderText="textbox">
<ItemTemplate>
<asp:TextBox ID="textbox_1" CssClass="textbox_1" runat="server" Text='<%# Eval("sql_textbox")%>'>
</asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</asp:TableCell>
</asp:TableRow>
And in the code behind:
foreach (GridViewRow row in gridview_1.Rows)
{
TextBox txtbox = ((TextBox)gridview_1.Rows[row.RowIndex].FindControl("textbox_1"));
txtbox.Attributes.Add("onkeypress","javascript:return validateFloatKeyPress(this, event);");
}
But when textboxes are generated, the JavaScript doesn't work. Why?
I can't do it in the ASP part, because I want the textboxes have different JavaScript methods with "if" clause in the code behind.
Thank you very much.

Answer 1

I put in asp:GridView the attribute onrowdatabound="GridView1_RowDataBound" and seems works properly. In code behind, I put...
<asp:GridView ID="gridview_1" DataSourceID="SqlDataSource3" AutoGenerateColumns="false" onrowdatabound="GridView1_RowDataBound" runat="server">
In code behind:
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.DataItem != null)
{
TextBox textBox1 = e.Row.FindControl("textbox_1") as TextBox;
textBox1.Attributes.Add("onkeypress","javascript:return validateFloatKeyPress(this, event);");
}
}
And it works properly, I think :)