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CONSTANT vs. READONLY in C#

by Rohit 29. March 2014 23:30

 CONSTANT

 

  1. CONST keyword is used to represent a CONSTANT. It is defined at compile-time and cannot be changed at run-time.
  2. Constants are declared as a field and the value must be initialized as they are declared:

 

Public const decimal BonusPercent = 5.25;

 

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.NET | C#

Resolving "Specified cast is not valid" error while seeking a row from DataTable.

by Rohit 22. December 2013 19:24

In a situation I had to create a Data Table manually and add columns and rows to it. Later I wanted to search for a row in this Data Table using LINQ. As soon as LINQ code was fired I got this error: "Specified cast is not valid". Below I am sharing a sample code to simulate this problem and will tell you how to get rid of this error in this particular situation I mentioned above.

Sample Code:

public partial class _Default : System.Web.UI.Page
    {
        DataTable dt = new DataTable();

        protected void Page_Load(object sender, EventArgs e)
        {

            dt.Columns.Add("RowId");
            dt.Columns.Add("Amount");

            DataRow row = dt.NewRow();
            row[0] = 1;
            row[1] = 2000;

            dt.Rows.Add(row);

            GetRecord(1);
        }

        protected void GetRecord(int RowId)
        {
            var results = from row in dt.AsEnumerable()
            where row.Field<int>("RowId") == RowId
            select row;

            string FetchedRowId = results.ToArray()[0].ToString();
        }
    }



If you execute this code, you will get this error:




The root of this error lies during the creation of columns for the Data Table. Do you notice these lines:

dt.Columns.Add("RowId");
dt.Columns.Add("Amount");


Here if you don't specify the Type of column, the default type considered is 'string'. Mentioning the default type of each column solves this issue:

dt.Columns.Add("RowId", typeof(int));
dt.Columns.Add("Amount", typeof(int));

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.NET | ASP.NET | C#

Visual Studio 2013 (First Look): One ASP.NET and BootStrap

by Rohit 15. December 2013 14:43

With the release of Visual Studio 2013 comes more improvements to make life of developers even more easier.  The release of Visual Studio 2013 came as a surprise though. Few weeks back I downloaded Visual Studio 2012 Express and was excited to start a new MVC application on it. I wanted to submit feedback and some valid reasons to migrate old projects to Visual Studio 2012 to my team in office. My feedback document now requires a revision with the release of 2013. No doubt, the changes looks exciting.

 

 Not only me but most developers wanted to use both MVC and Web Forms together in few situations. One ASP.NET is a move towards this. Visual Studio 2013 provides this option when you create a new Web Forms application.

 

 

If you select MVC in [Add folders and core references for:], Visual Studio 2013 creates a new project which includes MVC folders and default Web Forms as shown below: More...

About Rohit Prakash

Software Craftsman and Technology Enthusiast (not a Guru).

Technical Reviewer of a book on open-source programming IDE.

My day job keeps me engaged with Microsoft Technologies (ASP.NET, C# and SQL Server) hence most of the posts are related to these technologies. I, however, love to play with other open-source technologies. I also have interest in IT Security and therefore you will find posts on Malware Analysis, Cryptography and Anti-Virus programs.

Few people have contacted me for Guest Posts. You will find these posts as well.

 

You can reach me at:

rohit [at] irohitable.com

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