How to validate Textbox when Checkbox is checked in RadGrid using JavaScript

Question

How do you validate a textbox when a checkbox is checked in a RadGrid using JavaScript? I tried to use the CheckBox_CheckedChanged event but it is not working. Please tell me how to validate if the textbox is empty or not when a checkbox is checked in a RadGrid in ASP.NET.

C#:

protected void CheckBox1_CheckedChanged1(object sender, EventArgs e)
{           
    foreach (GridDataItem item in radGridSahreaJob.MasterTableView.Items)
    {
        TextBox txtMaxResumes = (TextBox)item.FindControl("txtMaxResumes");
        CheckBox chkBox = (CheckBox)item.FindControl("chkIsCandidateSelected");              
        string str = txtMaxResumes.Text;
        if (chkBox.Checked && string.IsNullOrEmpty(str))
        {
            ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "alert", "getMessagetest('ShareaJob');", true);
        }
    }
}

ASP.NET:

<Columns>
    <telerik:GridTemplateColumn UniqueName="chkSelect" lowFiltering="false">
        <HeaderTemplate>
            <asp:CheckBox ID="chkSelectAll" runat="server" OnClick="return SelectAllCandidates(this);" />
        </HeaderTemplate>
        <ItemTemplate>
            <asp:CheckBox ID="chkIsCandidateSelected" runat="server" OnClick="return CandidateRowChecked();" AutoPostBack="True" oncheckedchanged="CheckBox1_CheckedChanged1"/>
        </ItemTemplate>                                
    </telerik:GridTemplateColumn>
    <telerik:GridTemplateColumn HeaderText="Max.Resume(s) &nbsp;can upload" HeaderStyle-HorizontalAlign="Center" ShowFilterIcon="false" AllowFiltering="false">
        <ItemTemplate>
            <asp:TextBox ID="txtMaxResumes" runat="server" CssClass="rgf_txt_area_l2" Text="3" Width="80px" MaxLength="2">
            </asp:TextBox>
        </ItemTemplate>
    </telerik:GridTemplateColumn>
</Columns>

JavaScript:

 function getMessagetest(entity) {
     if (entity == 'ShareaJob') {
         radalert("Please enter number !", 370, 150, "Alert");
     }
 }

Answer 1

finally i got solution. Thanks.

 foreach (GridDataItem item in radGridSahreaJob.MasterTableView.Items)
            {
                CheckBox CheckBox1 = item.FindControl("chkIsCandidateSelected") as CheckBox;
                TextBox TextBox1 = item.FindControl("txtMaxResumes") as TextBox;
                string strTxtResumes = TextBox1.Text;
                if (CheckBox1 != null && CheckBox1.Checked && string.IsNullOrEmpty(strTxtResumes))
                {
                    hdnCheckBox.Value = "1"; 
                }
            }