I would like to read selected value from dropdownlist and accordingly, set the maxlength of a textbox through javascript.
To use javascript inside a user control, one should remember, while it is rendered in the page, a control called txtComany will be having a name like ctl03$txtComany when it is rendered on the page.
Hence it is important to call the clientId of the textbox like :
document.getElementById(“<%=txtComany.ClientID%>”).value;
function SetTextBoxMaxLength() {
var e = document.getElementById(“<%=DropDownlist1.ClientID%>“);
var strUser = e.options[e.selectedIndex].text;
if (strUser == “Cargo ” || strUser == “Agent”) {
//Set maxlength of textbox to 11 through Javascript
document.getElementById(“<%=TextBox1.ClientID%>“).maxLength = 11
}
else {
//Set maxlength of textbox to 8 through Javascript
document.getElementById(“<%=TextBox1.ClientID%>“).maxLength = 8
}
}
The HTML of the page is like
<asp:TextBox CssClass=”contact” ID=”CUECode” onKeyDown=”SetCUECodeMaxLength();” runat=”server”/>
To get selected value from dropdownlist using javascript:
var e = document.getElementById(“<%=Dropdown1.ClientID%>”);
var strUser = e.options[e.selectedIndex].text;
To use onchange event of dropdownlist instead of using the selectedindexchange event through code behind to prevent postback, suppose the HTML is as shown below:
}
