ASP.Net textbox onblur event

c# asp.net-3.5

79,279

Solution 1

In the Code behind: (VB.NET)

On the page load event

txtAccountNumber.Attributes["onBlur"] = "IsAccNumberValid(" & txtAccountNumber.ClientID & ")";

Where txtAccountNumber is the ID of the TextBox in the markup page and you pass the ClientID of the textbox because JavaScript is client side not server side. And now in the markup page(.aspx) have this javascript in the head section of the page:

<script type="text/javascript">                     
function IsAccNumberValid(txtAccountNumber) {                                             
    if (txtAccountNumber.value.length < 6) {    
                      alert(txtAccountNumber.value);
            }    
        }    
</script>

Solution 2

Is that the actual code in your Page_Load? You need to use the name of the control, and not the type name for TextBox. For example, you may want to try:

 textBox1.Attributes.Add("onblur", "validate();");

where "textBox1" is the ID you assigned to the textBox in your markup instead.

Also, from Javascript, it's very possible that the ID of the textBox has changed once it gets rendered to the page. It would be better if you would pass the control to the validate function:

function validate(_this)
{
    if (_this.value == "50")
        // then set the ID of the label.  
}

Then you would set the attribute like this:

textBox1.Attributes.Add("onblur", "validate(this);");

Lastly, I would strongly recommend using the JQuery library if you're doing anything in Javascript. It will make your life 10x easier.

Solution 3

This works.

Textbox1.Attributes.Add("onblur","javascript:alert('aaa');");

Make sure that functiion lies in the script part of the page.

My page

<script type="text/javascript">
    function Validate() {

        alert('validate');

    }

    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:TextBox ID="Textbox1" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="Button" />
    </div>
    </form>
</body>
</html>

code behind

public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Textbox1.Attributes.Add("onblur","Validate();");
        }
    }

79,279

Author by

LearningCSharp

(rogerc2) I am a newbie and in my learning stage.

Updated on August 25, 2020

Comments

LearningCSharp almost 4 years
I have a textbox, whose values I need to validate (if value of textbox is 50, then display message in lblShowMsg) when the user tabs out of the textbox (onBlur event). I can't seem to get the syntax right.

I have this code on my pageload event:
```
protected void Page_Load(object sender, EventArgs e)
{
    txtCategory.Attributes.Add("onblur", "validate()"); 

}
```
But I can't seem to get the javascript code correct. Any suggestions?
LearningCSharp over 14 years

Sorry, that was a typo on my part. The ID of the txtBox is txtCategory
LearningCSharp over 14 years

Don't need an alert; Need to display a msg in a label; (lblShowMsg.visible = true)
LearningCSharp over 14 years

When I run the code as you show it above (no JQuery), I get an error message "Microsoft JScript runtime error: 'document.form1.lblShowMsg' is null or not an object"
David Morton over 14 years

Again, part of the problem is that the label you're wanting to use is more than likely renamed to something else. Use something like Developer Tools in IE or FireBug in Firefox to hunt down the actual ID of the label on the form. Both of those tools will let you peck through the DOM. Once you find it, use document.getElementById("id of element here") to fetch the element, and then you can set it's innerHTML property in Javascript.
LearningCSharp over 14 years

I used Developer Tools, and I can see that the label has the same ID value of lblFSCText; I would think that such a basic functionality of validating onblur, wouldn't be so complicated in such an advanced language;
David Morton over 14 years

document.getElementById("lblFSCText").innerHTML = "Valid";
LearningCSharp over 14 years

didn't work. Still getting the document.getElementByID(...) is null or not an object; I understand what you mean by the object being renamed to anothr ID, but in Dev Tools, it does have the same ID.
Danimal111 over 10 years

Here is the C# Version: ddlCompanies.Attributes["onBlur"] = "AddNewCompany1(" + ddlCompanies.ClientID + ")";
fletchsod about 4 years

JQuery is being depreciated or obsolete now. Just a FYI!