Theres is no any event availabe for the OnMouseOver in Calendar Conrol but you can do this by Using OnSelectionChange event of calendar
<form id="form1" runat="server">
<div>
<asp:Calendar ID="cDate" runat="server" OnSelectionChanged="cDate_OnSelectionChanged">
</asp:Calendar>
</div>
</form>
C#:
protected void cDate_OnSelectionChanged(object sender, EventArgs e)
{
string date = cDate.SelectedDate.ToString("dd/MM/yyyy");
//Pass this date for searching into the Database
//code for searching in database
// if found then show the alert message
string message = "Your Event Details";
System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append("<script type = 'text/javascript'>");
sb.Append("window.onload=function(){");
sb.Append("alert('");
sb.Append(message);
sb.Append("')};");
sb.Append("</script>");
ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());
}
Thank You.
