Implement Change Password Feature in ASP.Net with example

hi

 i have 3 textbox 1 button and in my change password.aspx

1-Txtold== user should enter their old password 

2-Txtnew1== usershould enter their new password 

3-Txtnew2==user should retype their new password

and House_info table

Now i want when users click on button at first check that Txtold value if that was equal with password column it will change password column with  Txtnew1 value

i wrote below code

    protected void Imgpass_Click(object sender, ImageClickEventArgs e) { string data=Server.UrlDecode(Request.QueryString["Behcode"]); SqlCommand _cmd=new SqlCommand("changepassword",_cn); _cmd.CommandType=CommandType.StoredProcedure; _cn.Open(); _cmd.Parameters.AddWithValue("@behcode",data); _cmd.Parameters.AddWithValue("@Oldpass",Txtold.Text); _cmd.Parameters.AddWithValue("@Newpass",Txtnew1.Text); _cmd.ExecuteNonQuery(); Session["Message"] = true; Response.Redirect(Request.Url.AbsoluteUri); _cn.Close(); } 

SP

create procedure dbo.changepassword @behcode nvarchar(10) ,@Oldpass nvarchar(20) ,@Newpass nvarchar(20) as begin update House_info set password=@Newpass where  BehCode=@behcode and password=@Oldpass end 

it worked correctly but i want if users don't enter their old password in Txtold textbox correctly  it show message that for changing password they should enter their old password correctly

how i can do it

 thanks