Arithmetic parser in Javascript

I just added an arithmetic parser in Javascript code sample on Github, check out the following repo: JsSimpleParser The parser is also available through Npm: https://www.npmjs.com/package/simplejsparsermatharithmetic Installation: npm i simplejsparsermatharithmetic Supported expressions (examples): 2+3 should evaluate to 5 12 * 5–(5 * (32 + 4)) + 3 should evalute to -117 This is a great example of how to write a parser of your own.

Using TagBuilder in MVC

I have been started programming MVC again at work after many years focusing more on WPF. So I came accross a class called 'TagBuilder'. This is a handy class for generating markup programatically. Let us create a HTML helper that renders an image tag. It can use TagBuilder to achieve this. First off, we create the HTML helper like this:

using System.Web;
using System.Web.Mvc;

namespace HelloTagBuilderDemo.Helpers
{
    /// <summary>
    /// Sample usage of TagBuilder in MVC
    /// </summary>
    public static class HtmlHelpers
    {
        /// <summary>
        /// Generates an IMG element which is self-closing and uses as src the given path pointing to an image file with a relative path within the web application
        /// and with alternate text
        /// </summary>
        /// <param name="path"></param>
        /// <param name="alternateText"></param>
        /// <returns></returns>
        // ReSharper disable once UnusedParameter.Global
        // ReSharper disable once InvalidXmlDocComment
        public static IHtmlString Image(this HtmlHelper htmlHelper, string path, string alternateText)
        {
            var builder = new TagBuilder("img");
            // ReSharper disable once StringLiteralTypo
            builder.Attributes.Add("src", VirtualPathUtility.ToAbsolute(path));
            builder.Attributes.Add("alt", alternateText);
            var markupResult = builder.ToString(TagRenderMode.SelfClosing);
            return new MvcHtmlString(markupResult);
        }
    }
}

We make use of the VirtualPathUtility.ToAbsolute method to convert a virtual path to an absolute path. Then we make use of the html helper inside a MVC view like this:

@{
    ViewBag.Title = "Home Page";
}

@using System.Web.Mvc.Html
@using HelloTagBuilderDemo.Helpers


<div class="jumbotron">
    <h1>ASP.NET</h1>
    <p class="lead">ASP.NET is a free web framework for building great Web sites and Web applications using HTML, CSS and JavaScript.</p>
    <p><a href="https://asp.net" class="btn btn-primary btn-lg">Learn more »</a></p>
</div>

<div class="row">
    <div class="col-md-4">
        <h2>Getting started</h2>
        <p>Harold is at it again, making clones of himself to inflict multiple pain.</p>                
    </div>
    <div class="col-md-4">
        @Html.Image(@"~/Images/haroldatitagain.jpg", "Harold")
    </div>
</div>

And now we have our resulting HTML helper at display, showing also in the screen grab the markup the HTML helper generated for us. [1] Tagbuilder on MSDN: https://docs.microsoft.com/en-us/dotnet/api/system.web.mvc.tagbuilder?view=aspnet-webpages-3.2

Deleting a set of databases with similar names with T-SQL

Devops Sunday. If you end up having many databases in SQL Server and want to get rid of them by matching their names, this T-SQL should help you out.

use master
go
declare @tablestoNuke as table(db nvarchar(100))
insert into @tablestoNuke
select name from sys.databases  
where name like '%SomeSimilarDbNameSet%'
declare @nukedb as nvarchar(100)
declare @nukesql as nvarchar(150)

declare nuker cursor for
select db from @tablestoNuke

open nuker
fetch next from nuker into @nukedb

while @@FETCH_STATUS = 0 
begin
set @nukesql = 'drop database ' + @nukedb
exec sp_executesql @nukesql
fetch next from nuker into @nukedb
end

close nuker
deallocate nuker

print 'All done nuking'

The T-SQL uses a cursor to loop through the database names fetched from sys.databases view on master db and then uses exec sp_executesql to delete the databases, by dropping them.