How to validate an Ajax control combo box has item selected or not?

First, you need to insert beside the combo box a custom validator like this,

<asp:CustomValidator ID="cv" runat="server" ControlToValidate="cmb" Text="*" ForeColor="Red" ValidateEmptyText="true" ClientValidationFunction="CustomValidator" Display="Dynamic" ErrorMessage="combo box is required!" CssClass="validator" ValidationGroup="valGrp"></asp:CustomValidator>

If your combo box default selected value is an empty string then you need to add a function inside a <script type="text/javascript"> like this,

    function CustomValidator(s, e) {

        if ($find(s.controltovalidate)._textBoxControl.value == "") {

            e.IsValid = false;

        }

    }

If your combo box default value of “Please select” then you need to add a function inside a <script type="text/javascript”> like this,

    function CustomValidator(s, e) {

        if ($find(s.controltovalidate)._textBoxControl.value == "Please select") {

            e.IsValid = false;

        }

    }

References used:

http://blog.csdn.net/ywuwgij/article/details/4617140

How fix the column width in a gridview at insert tooltip in each cell in Asp.net 4?

If you need to set the width of each column in a gridview control,  If the column is just to display and no editing needed. You can like this,

<asp:TemplateField HeaderText="column Name" SortExpression="fieldname">

<HeaderTemplate>

       <div style="text-align:center;background-color:#41627E;color:White;font-size:x-small;font-weight:bold;overflow: hidden;white-space: nowrap;width: 50px;" >column Name</div>

</HeaderTemplate>

<ItemTemplate>

<div style="font-size:xx-small;white-space:nowrap;overflow: hidden;text-align:left;font-weight:600;font-family:Tahoma;width: 50px;" >

 <asp:Label ID="lblGridColumnName" runat="server" Text='<%# Bind("fieldname") %>' ></asp:Label>

</div>

</ItemTemplate>

</asp:TemplateField>

But if there is a editing to be done, you need to do like this,

<asp:TemplateField HeaderText="column Name" SortExpression="fieldname">

<HeaderTemplate>

<div style="text-align:center;background-color:#41627E;color:White;font-size:x-small;font-weight:bold;overflow: hidden;white-space: nowrap;width: 40px;" >column name</div>

</HeaderTemplate>

<ItemTemplate>

<div style="font-size:xx-small;white-space:nowrap;overflow: hidden;text-align:left;font-weight:600;font-family:Tahoma;width: 40px;" >

<asp:Label ID="lblGridColumnName" runat="server" Text='<%# Bind("fieldname", "{0:n0}") %>'></asp:Label>

</div>

</ItemTemplate>

<EditItemTemplate>

              <asp:TextBox ID="txtGridColumnName" runat="server" Text='<%# Eval("fieldname", "{0:n0}") %>' Width="50px" CssClass="cssclass" />

       </EditItemTemplate>

</asp:TemplateField>

If you need insert a tooltip for each cell inside a gridview, you need to set each column tooltip. You can do like this,

protected void gv_DataBound(object sender, EventArgs e)

{

Label lbl = new Label();

foreach (GridViewRow rv in gv.Rows)

{

lbl = (Label)rv.FindControl("lblGridColumnName ");

rv.Cells[1].ToolTip = lbl == null ? string.Empty : lbl.Text;

}

}