I have a method in Serverside validaNIF and want to call it through javascript (Clientside) to validate an Asp:textbox when it does Leave

Question

I tried to do through the event ontextchange and call the backend function, only as this is to make a record, whenever it ran the event wipes the data from my other textboxs (it seems to refresh the page). Just getting the data from the textbox I’ve been validating(nif).

public void validaNif(object sender, EventArgs e){

    .....

}

Answer 1

Here you have two points with different solutions, if your problem is the imperviousness of the data after the postback of a control, this can be solved with the ViewState.

Now, objectively on the question of how to execute a code-Behind method via Javascript, there is a cake recipe for this, but with a more restricted application, it would be necessary to create a static method defined as [WebMethod], that besides having a peculiar configuration for its operation, you will not be able to handle other ASP components of your page on the server side.

First, check that on your.Master Site, there is already a component <asp:ScriptManager> declared, if the answer is yes, just add the attribute EnablePageMethods="true"

<form runat="server">
    <asp:ScriptManager runat="server" EnablePageMethods="true">
        <Scripts>
            //...
        </Scripts>
    </asp:ScriptManager>
    <!-- resto do conteúdo -->
</form>

Done that, you can add the [WebMethod] static for validation on your aspx. Since this method does not have a connection with the rendered components on the screen, instead of a void ValidarNif() will get a return bool and will receive an input parameter of type string.

[System.Web.Services.WebMethod]
public static bool ValidaNif(string nif)
{
    //no lugar dessa linha você aplicará as suas regras
    return string.IsNullOrWhiteSpace(nif);
}

If everything worked so far, when rendering the page and accessing the browser console, you will notice that there is an object PegeMethods initialized, as well as a representation of your method with the following signature ValidaNif(nif, onSuccess, onFailure, userContext)

You can invoke this method through the `Pagemethods', remembering to indicate the base path.

<script type="text/javascript">

    PageMethods.set_path('/SuaPagina.aspx'); //Precisa ser definido apenas uma vez

    PageMethods.ValidaNif('teste', //Valor que você vai capturar do TextBox
                       onSuccess = function(res){alert(res);},
                       onFailure = function(res){alert('error:' + res);}
                      );
</script> 

If you receive an error message with status 401 (Unauthorized), in your project browse App_start and edit the file RouteConfig.cs altering the AutoRedirectMode for Off

public static class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        var settings = new FriendlyUrlSettings();
        //settings.AutoRedirectMode = RedirectMode.Permanent;
        settings.AutoRedirectMode = RedirectMode.Off;
        routes.EnableFriendlyUrls(settings);
    }
}