Javascript validation not working in c#

Question

Here is the javascript validation code:

function ValidateFrom() {

if (document.getElementById("<%=txtCategoryName.ClientID %>").value.trim() == "") {

document.getElementById("<%=dvMessage.ClientID %>").innerHTML = "Please enter Category.";

document.getElementById("<%=txtCategoryName.ClientID %>").focus();

document.getElementById("<%=txtCategoryName.ClientID %>").classList.add("ErrorControl");

// document.getElementById("<%=txtCategoryName.ClientID %>").style.outline = '1px solid red';

// document.getElmentById("<%=txtCategoryName.ClientID %>").style.border = '3px solid red';

return false;

}

if (document.getElementById("<%=txtCategoryDescription.ClientID %>").value.trim() == "") {

document.getElementById("<%=dvMsg.ClientID %>").innerHTML = "Please enter Category Description.";

document.getElementById("<%=txtCategoryDescription.ClientID %>").focus();

document.getElementById("<%=txtCategoryDescription.ClientID %>").classList.add("ErrorControl");

// document.getElementById("<%=txtCategoryDescription.ClientID %>").style.outline = '1px solid red';

return false;

}

}

 

 

 

 

<script>

function checkfunction(val) {

if (val != "") {

document.getElementById("<%=txtCategoryName.ClientID %>").classList.remove("ErrorControl");

// document.getElementById("<%=dvMessage.ClientID %>").style.display = 'none';

document.getElementById("<%=txtCategoryDescription.ClientID %>").classList.remove("ErrorControl");

// document.getElementById("<%=dvMsg.ClientID %>").style.display = 'none';

}

}

</script>

 

 

Here is the text box:

<div class="field">

<div id="dvMessage" runat="server" style="color: Red" >

</div>

<label>

Category Name <em>*</em>

</label>

<div>

<asp:TextBox ID="txtCategoryName" runat="server" CssClass="form-01-control" onkeyup="checkfunction(this.value)" placeholder="Enter Category Name" ></asp:TextBox>

</div>

<div id="dvMsg" runat="server" style="color: Red">

</div>

<label>

Category Description <em>*</em></label>

<div>

<asp:TextBox ID="txtCategoryDescription" runat="server" CssClass="form-01-control" onkeyup="checkfunction(this.value)" placeholder="Enter Category Description"></asp:TextBox>

</div>

<label>

Parent Category </label>

<div>

<asp:DropDownList ID="ddlParentCategory" runat="server" Width="250px" class="form-01-control">

</asp:DropDownList>

</div>

<label>

Category Image</label>

<div>

<asp:FileUpload ID="fuImage" runat="server" />

<asp:Image ID="imgCategory" Width="100" Height="100" runat="server" />

</div>

</div>

 

The problem is that validation not working properly... The ERROR MESSAGE having problem..