we can display alert box from asp.net code-behind that is

1. ScriptManager.RegisterStartupScript(this,GetType(),"alertmsg","alert('hahahahah');",true);

below mention script how to write on button click with server side confirmation in asp.net

Response.Write("")

///

/// showAlert///

public string showAlert(string msg){string message = msg;System.Text.StringBuilder sb = new System.Text.StringBuilder();sb.Append("");return sb.ToString();} and then call above function likeClientScript.RegisterClientScriptBlock(this.GetType(), "alert",showAlert("Student already admitted to this batch."));

page.registerstartupscript("sss","alert('student details not avlible')");

Page.RegisterStartupScript("ddd", "alert('student details not avalible')");

Page.RegisterStartupScript("ddd", "alert('student details not avalible')");

Response.Write("alert('Duplicate files not allowed');");

Response.Write("javascript:alert('Your message');");

alert("message");

You need to drag script manager and then type the follwing code wherever u required

ClientScript.RegisterClientScriptBlock(typeof(Page), "test", "");

Response.Write("alert('Hello');");

Write this line of code to diplay the alert message. Response.Write("alert('Hello Puru!!!')");