ASP.NET单选按钮检查已更改的事件未触发第一个单选按钮

Question

I am facing an issue where the checked changed event of the first radio button is not firing. I enabled ViewState but still the issue persists. Please see below code:

<span class="pull-right text-right">
    <label class="inline radio">
        <asp:RadioButton runat="server" ID="rdoViewAll" CausesValidation="false" GroupName="Filter" Text="View All" AutoPostBack="true" EnableViewState="true" Checked="true" />
    </label>
    <label class="inline radio">
        <asp:RadioButton runat="server" ID="rdoViewCurrent" CausesValidation="false" GroupName="Filter" Text="View Current" AutoPostBack="true" />
    </label>
    <label class="inline radio">
        <asp:RadioButton runat="server" ID="rdoViewFuture" CausesValidation="false" GroupName="Filter" Text="View Future" AutoPostBack="true" />
    </label>
</span>

And I am setting the checked changed event on Page_Init as below:

public void Page_Init(object sender, EventArgs e)
{
    this.rdoViewAll.CheckedChanged += (s, a) =>
    {
        RebindTerms();
    };
    this.rdoViewFuture.CheckedChanged += (s, a) =>
    {
        RebindTerms();
    };
    this.rdoViewCurrent.CheckedChanged += (s, a) =>
    {
        RebindTerms();
    };
}

One thing I noticed is when I remove the Checked="true" property on the first radio button the CheckedChanged event fires successfully. However, I need the first radio button to be checked by default on page load.

Answer 1

You can leave Checked="false" for all the RadioButtons initially, and set the selected button with client code:

private RadioButton selectedRadioButton;

protected void Page_Load(object sender, EventArgs e)
{
    selectedRadioButton = rdoViewAll;

    if (rdoViewCurrent.Checked)
    {
        selectedRadioButton = rdoViewCurrent;
    }

    if (rdoViewFuture.Checked)
    {
        selectedRadioButton = rdoViewFuture;
    }

    rdoViewAll.Checked = false;
    rdoViewCurrent.Checked = false;
    rdoViewFuture.Checked = false;

    ClientScript.RegisterStartupScript(GetType(), "InitRadio", string.Format("document.getElementById('{0}').checked = true;", selectedRadioButton.ClientID), true);
}

Clicking on any RadioButton will always trigger the CheckedChanged event. The RadioButton that is actually selected is stored in selectedRadioButton , if you need it in other parts of the server code.