Custom Validator in a Composite Control not firing

Hello everyone,
I am badly stuck in middle of project with this issue. Googled a lot but not getting a solution.
 
My objective is to create a composite control with a label, textbox, two required field validator and a custom validator. My custom control code is as follows:-

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
 
namespace AFGISServerControl
{
    [ToolboxData("<{0}:ValidatorTextBox runat="\""server\"> </{0}:ValidatorTextBox>")]
    public class ValidatorTextBox : CompositeControl
    {
        private TextBox InputTextBox;
        private Label InputLabel;
        private RequiredFieldValidator RequiredValidator1;
        private RequiredFieldValidator RequiredValidator2;
        private CustomValidator cv;
        private static readonly object EventValidateKey = new object();
 
        protected override void OnLoad(EventArgs e)
        {
            EnsureChildControls();
            base.OnLoad(e);
        }
        protected override void CreateChildControls()
        {
            Controls.Clear();
            InputTextBox = new TextBox();
            InputLabel = new Label();
            InputTextBox.ID = "inputTextBox";
            //InputTextBox.AutoPostBack = true;
 
            RequiredValidator1 = new RequiredFieldValidator();
            RequiredValidator1.ID = this.ID + "_RFV1";
            RequiredValidator1.ControlToValidate = InputTextBox.ID;
            RequiredValidator1.ValidationGroup = string.Empty;
            RequiredValidator1.Display = ValidatorDisplay.Dynamic;
            RequiredValidator1.ErrorMessage = Caption.ToString() + " is mandatory";
 
            RequiredValidator2 = new RequiredFieldValidator();
            RequiredValidator2.ID = this.ID + "_RFV2";
            RequiredValidator2.ControlToValidate = InputTextBox.ID;
            RequiredValidator2.Display = ValidatorDisplay.Dynamic;
            RequiredValidator2.ErrorMessage = Caption.ToString() + " is mandatory";
 
            cv = new CustomValidator();
            cv.ID = this.ID + "_CV";
            cv.ControlToValidate = InputTextBox.ID;
            cv.SetFocusOnError = true;
            cv.Display = ValidatorDisplay.Dynamic;
            cv.ErrorMessage = this.CustomErrorMessage;
            cv.ValidateEmptyText = true;
            cv.ServerValidate += new System.Web.UI.WebControls.ServerValidateEventHandler(this.cv_ServerValidate);
           
            this.Controls.Add(InputLabel);
            this.Controls.Add(InputTextBox);
            this.Controls.Add(RequiredValidator1);
            this.Controls.Add(RequiredValidator2);
            this.Controls.Add(cv);
        }
 
        #region properties
        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("Value")
        ]
        public string Text
        {
            get
            {
                EnsureChildControls();
                return InputTextBox.Text;
            }
            set
            {
                EnsureChildControls();
                InputTextBox.Text = value;
            }
        }
        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("Validation Group")
        ]
        public string ValidationGroup
        {
            get
            {
                EnsureChildControls();
                return InputTextBox.ValidationGroup;
            }
            set
            {
                EnsureChildControls();
                InputTextBox.ValidationGroup = value;
                RequiredValidator2.ValidationGroup = value;
                cv.ValidationGroup = value;
            }
        }
        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("Error message for the custom validator.")
        ]
        public string CustomErrorMessage
        {
            get
            {
                EnsureChildControls();
                return cv.ErrorMessage;
            }
            set
            {
                EnsureChildControls();
                cv.ErrorMessage = value;
            }
        }
        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("Validity of custom validator.")
        ]
        public Boolean isValid
        {
            get
            {
                EnsureChildControls();
                return cv.IsValid;
            }
            set
            {
                EnsureChildControls();
                cv.IsValid = value;
            }
        }
 
        [
        Bindable(true),
        Category("Default"),
        DefaultValue(""),
        Description("The text for the name label.")
        ]
        public string Caption
        {
            get
            {
                EnsureChildControls();
                return InputLabel.Text;
            }
            set
            {
                EnsureChildControls();
                InputLabel.Text = value;
            }
        }
        #endregion
 
        protected override void RecreateChildControls()
        {
            EnsureChildControls();
        }
 
        [
        Category("Action"),
        Description("Raised on Text Change")
        ]
        public event ServerValidateEventHandler Validate
        {
            add
            {
                Events.AddHandler(EventValidateKey, value);
            }
            remove
            {
                Events.RemoveHandler(EventValidateKey, value);
            }
        }
        protected virtual void OnValidate(ServerValidateEventArgs args)
        {
            EventHandler ValidateHandler = (EventHandler)Events[EventValidateKey];
            if (ValidateHandler != null)
            {
                ValidateHandler(this, args);
            }
        }
        protected void cv_ServerValidate(object source, ServerValidateEventArgs args)
        {
            OnValidate(args);
        }
 
        protected override void Render(HtmlTextWriter writer)
        {
            AddAttributesToRender(writer);
            InputLabel.RenderControl(writer);
            InputTextBox.RenderControl(writer);
            RequiredValidator1.RenderControl(writer);
            RequiredValidator2.RenderControl(writer);
            cv.RenderControl(writer);
        }        
    }
}

 
My aspx code is

<cc1:ValidatorTextBox ID="ValidatorTextBox1"  runat="server" LabelText="Service No" CustomErrorMessage="Not Valid" ValidationGroup="test"  önValidate="CVText" />
<asp:Button ID="Button1" runat="server" Text="Button" />

 
The specific issue faced are
- Code behind method for "onvalidate" event is not being fired
- Required field validator error message is displaying only "is mandatory", the caption is not prefixed.
 
I will be greatful for the advice.