I found this question very interesting. Since majority of the time we focus on implementation of a feature. We discuss how a particular feature can be implemented in greater extent but we tend to forget in which version of C Sharp that particular feature got introduced. For a junior level programmer interview, this could be a vital question that list different features of C Sharp version wise. I am trying to answer this question pictorially below,

I am sure taking a high level look on this picture before going to interview could be a help. I hope you find this picture post useful. Thanks for reading.

C Sharp 4.0 introduced Optional Parameter feature . According to this feature, in function call only required parameters are needed to be passed. If value of Optional Parameters are not provided then they will take default constant value. To understand it better, let us take following function as example.

static void Display(string Name, int age,string Nationality="Indian")
{

Console.WriteLine("Hey " + Name + " you are " + age + " old " + Nationality);
}

In function Display, Nationality is an optional parameter. So while calling this function you will get intellisense suggesting you that if not provided parameter Nationality will take constant string value “Indian”

You can call Display function omitting value of parameter Nationality as following

static void Main(string[] args)
{
Display("dj", 28);
Console.ReadKey(true);

}

In output you will notice that value of parameter Nationality is set to default string constant “Indian”

 
Now you can see that Optional Parameters has taken the default constant value. C# 5.0 gives us liberty or allow us to attribute optional parameter with caller info attributes. By providing caller info attributes at the runtime optional parameter value will be replaced by dynamic values for caller info attributes. There are three caller info attributes are available,

Let us go ahead and rewrite Display function with Method Caller Information attribute on optional parameters.

You see in above function definition [see the rectangle], we have attributed three optional parameters with method caller information. We can display method caller information as following,

static void Display(string Name,
int age,
string Nationality="Indian",
[CallerMemberName] string Caller = "",
[CallerFilePath] string file="",
[CallerLineNumber] int line=0)
{

Console.WriteLine("Hey " + Name + " you are " + age + " old " + Nationality);
Console.WriteLine("This function is called  from member " + Caller + " file " + file + " line " + line);
}

Now when you call the function you will get method caller information printed. Expected output would be as following

 
Method Caller Information is particularly very useful in logging of the application. For high level logging, I would consider using Method Caller Information attributes along with optional parameters. I hope you find this post on Method Caller Information in C# 5.0 useful. Thanks for reading.

After talking to him, I thought why not to blog about it? I am trying here to use minimum words and optimum code samples can be discussed with interviewer as answer of this question.

Action is type of delegate

1. It returns no value.
2. It may take 0 parameter to 16 parameters.

For example below Action can encapsulates a method taking two integer input parameter and returning void.

So if you have method like below,

You can encapsulate method Display in Action MyDelegate as below,

An Action with one input parameter is defined in System namespace as below,

Where in T is type of input parameter and T obj is value passed for the parameter.

Action with Anonymous method

You can work with Action and anonymous method as well. You can assign anonymous method to Action as below,

Above code will print 9 as output.

Action with Lambda Expression

Like any other delegates, Action can be worked with lambda expression also as below,

Above code will also print 9 as output.

Passing Action as input parameter

You can pass Action as parameter of a function also. Let us say you have a class

And two functions called Display and Show to display Name and RollNumber of Student.

Now you got a function where you need to pass either Display or Show. Or in other words you need to pass any function with the same signature of Display or Show. In that case you will be passing a delegate as input parameter to the function.

You can call CallingAction method in Main as below,

Above we are creating instance of Student class and one by one passing Display function and Show function as input parameter to CallingAction function. In CallingAction function, we are printing name of the function being passed as input parameter. On running you will get below output.

I hope now you would be able to answer what is Action in simple words. I hope this post is useful. Thanks for reading.

Start MongoDB server

If you would have gone through MongoDB on Windows quick start in 5 minute then you know how to start MongoDB server. However just for quick recap you need to start MongoDB server as below,

You can connect to MongoDB server as below by executing mongod exe

By default MongoDB stores data inside data folder of C Drive. You need to explicitly create this folder as well.

Add required library in solution

You will get a solution when you download MongoDB for CSharp from here . Open the solution in Visual Studio and build it.

Take MongoDB.dll and add this reference to your project.

Create Project and perform operations

For purpose of this blog post, I am going to create a console application. I have added MongoDB.dll as reference in console application project.

Create DataBase

If you want to create a database, you can create as below,

Above code will connect to MongoDB and create a database called Bloggers, if it does not exist.

Add Record in DataBase

You can add record as below,

Where blogger is collection you get over database as below,

Delete Record from DataBase

You can delete a record by just providing one key value as well like below,

Fetch a Record

To fetch a particular document or record you need to create document and provide key value as below.

FindOne() function returns a document . You need to call Get function with key value as input to fetch the value.

For your reference full source code is as below,

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MongoDB;

namespace ConsoleApplication34
{
class Program
{
static void Main(string[] args)
{

//Create Database
Mongo mongoDBdataBase = new Mongo();
mongoDBdataBase.Connect();
var dataBaseToWork = mongoDBdataBase.GetDatabase("Bloggers");
//Create Collection
var blogger = dataBaseToWork.GetCollection("blogger");

//Insert Records
var b = new Document();
b["Name"] = "Dhananjay";
b["Country"] = "India";
blogger.Insert(b);
b["Name"] = "G Block";
b["Country"] = "USA";
blogger.Insert(b);

//Fetch Record
var searchBlogger = new Document();
searchBlogger["Name"] = "Dhananjay";
var result = blogger.FindOne(searchBlogger);
Console.WriteLine(result.Get("Country").ToString());

Console.ReadKey(true);

}
}
}

In this way you can perform operations on MongoDB using CSharp. I hope this post is useful. Thanks for reading.

In this post, let us try to do the reverse process. We will read all the rows of Excel file List of Bloggers. Again start with creating the custom class

Create Entity class

Add namespace

Setting initial code as of Excel template

I will walkthrough line by line of codes to make you easier for you to get a sense of the code.

In above code snippet last three lines should appear easier to you. However in first line of code you might be thinking, “Hey why string array of length 4? “ Answer of this that, if you notice our excel file it is having four columns. So in our logic we need a string array of four. If you are working with excel file with columns 10 then your string array should of size 10.

Then I have list of bloggers and each blogger object will represent a row of the excel file.

Open Excel file

If you have save template Excel file with different name in different location then you will have to change the location in above code.

If you have changed the sheet name to item then you will fetch it as below,

If you have not renamed the sheet and want to insert in the first sheet, you can do like below. Make note of code in comment to fetch the first sheet.

Read Row by Row

In above code snippet

1. We are iterating through all the rows in open sheet.
2. Iterating through all the cells on selected rows.
3. There is a check because we don’t want to read first row. Since first row of the excel will contain headers not the real data.

If all the cells contains numeric value then above code is suffice but there may be string or Boolean values as well. So we need to check that also as below,

Checking for string cell values

Checking for Boolean cell values

Set the value in string array as below,

Now we need to create object of Bloggers class by values from string array.

Consolidating all together we can create a function to read excel file

static List<Bloggers> ReadExcelFileDOM(string filename)
{

string[] strProperties = new string[4];
List<Bloggers> lstBloggers = new List<Bloggers>();
Bloggers facet = null;
int j = 0;

using (SpreadsheetDocument myDoc = SpreadsheetDocument.Open(filename, true))
{
WorkbookPart workbookPart = myDoc.WorkbookPart;
IEnumerable<Sheet> Sheets = myDoc.WorkbookPart.Workbook.GetFirstChild<Sheets>().Elements<Sheet>().Where(s => s.Name == "items");
if (Sheets.Count() == 0)
{
}
string relationshipId = Sheets.First().Id.Value;
WorksheetPart worksheetPart = (WorksheetPart)myDoc.WorkbookPart.GetPartById(relationshipId);
SheetData sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();

List<string> lstRow = new List<string>();

int i = 1;
string value;
foreach (Row r in sheetData.Elements<Row>())
{
if (i != 1)
{
foreach (Cell c in r.Elements<Cell>())
{
if (c != null)
{
value = c.InnerText;

if (c.DataType != null)
{
switch (c.DataType.Value)
{
case CellValues.SharedString:
var stringTable = workbookPart.GetPartsOfType<SharedStringTablePart>().FirstOrDefault();
if (stringTable != null)
{
value = stringTable.SharedStringTable.
ElementAt(int.Parse(value)).InnerText;
}
break;
case CellValues.Boolean:
switch (value)
{
case "0":
value = "FALSE";
break;
default:
value = "TRUE";
break;
}
break;
}
}

strProperties[j] = value;
j = j + 1;
}

}
}
j = 0;
&nbsp;

i = i + 1;
facet = new Bloggers();
facet.Name = strProperties[0];
facet.Intrest = strProperties[1];
facet.NumberofPosts = strProperties[2];
facet.Speaker = strProperties[3];
lstFacetToInsert.Add(facet);
}

return lstFacetToInsert;
}

}

And you can make function call as below,

List<SCDataFacets> result =  ReadExcelFileDOM("D:\\MyExcel.xlsx");

foreach (var a in result)
{

Console.WriteLine(a.Name);

}
Console.ReadKey(true);

This was all required to read a excel file using Open XML SDK. I hope this post was useful to you. Thanks for reading

If you find my posts useful you may like to follow me on twitter http://twitter.com/debug_mode or may like Facebook page of my blog http://www.facebook.com/DebugMode.Net If you want to see post on a particular topic please do write on FB page or tweet me about that, I would love to help you

You can download it from below URL

http://www.microsoft.com/download/en/details.aspx?id=5124

Once you download and run the MSI follow the below steps.

Creating Data Source to be inserted in excel

Let us say you have class as below,

And below function returning list of bloggers. We are going to insert all the items from this list in Excel file.

private List<Bloggers> GetDataToInsertInExcel()
{
List<Bloggers> lstBloggers = new List<Bloggers>
{
new Bloggers
{
Name = "Pinal Dave",
Interest = "SQL Server",
NumberofPosts = 1500,
Speaker = true
},
new Bloggers
{
Name = "Mahesh Chand",
Interest = "C Sharp",
NumberofPosts = 1300,
Speaker = true
},
new Bloggers
{
Name = "Debug Mode",
Interest = "all",
NumberofPosts = 400,
Speaker = false
},
new Bloggers
{
Name = "Shiv Prasad Koirala",
Interest = "ASp.Net",
NumberofPosts = 500,
Speaker = true
},
new Bloggers
{
Name = "Anoop Madusudhan",
Interest = "WCF",
NumberofPosts = 500,
Speaker = false
},
};
return lstBloggers;
}

&nbsp;

&nbsp;

You are very much free to change data source to

• Azure table
• SQL Server table
• SQL Azure table

Theoretically you can use any data source provided you are converting the result in List. If you are using SQL Server or SQL Azure, you can use LINQ to SQL to create data source.

Since now we have data source, let us insert the items of list in the excel file using open xml SDK.

Add Namespaces

You need to add below namespaces,

Have a Template

If you notice we have four properties in entity class. So there would be four columns in the excel sheet. Save an excel file with any name of your preference at any location of your preference. For purpose of this article I am saving it to the

There are three points worth noticing about the template

1. All the columns [properties of entity class] is in first row in columns A, B,C,D
2. Sheet is renamed to items. If you want you can have default name.
3. Template excel file with name testupload is in d drive.

Opening the template file to insert rows

If you have save template Excel file with different name in different location then you will have to change the location in above code.

If you have changed the sheet name to item then you will fetch it as below,

If you have not renamed the sheet and want to insert in the first sheet, you can do like below. Make note of code in comment to fetch the first sheet.

Inserting the rows

Now document is open, so we need to insert rows one by one. So we will loop through all the items in list and call a function to create row. On successful return of the row from function we will append it to the open sheet.

If you notice above code snippet I have initialized index value to 2 because in first row of the excel sheet, we are putting the header. From second row onward items in each row would get inserted. I am making call to CreateContentRow function.

Creating the rows

In you notice above that in header columns string array, we are starting from A to D. It is because we have only four columns to insert. If you have 6 columns to insert then string array would be from A to F.

In above snippet I am iterating through all the properties of the entity object and creating cell reference by appending index with column headers.

Next I need to find type of property .There may be three types

1. String
2. Integer
3. Boolean

We need to check for the type of property and then create the cell to insert the value

Checking for String

Checking for Integer

Checking for Boolean

Putting all together all pieces of codes we discussed above, for your reference whole source code is as below,

using System;
using System.Collections.Generic;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;

namespace ConsoleApplication28
{
class Program
{
static void Main(string[] args)
{
CreatingAndUploadingExcel();
}
Public static bool CreatingAndUploadingExcel()
{

using (SpreadsheetDocument myWorkbook = SpreadsheetDocument.Open("d:\\LocalCollection.xlsx", true))
{
//WorksheetPart worksheetPart = workbookPart.WorksheetParts.First();

WorkbookPart workbookPart = myWorkbook.WorkbookPart;

IEnumerable<Sheet> Sheets = myWorkbook.WorkbookPart.Workbook.GetFirstChild<Sheets>().Elements<Sheet>().Where(s=>s.Name=="items");
if (Sheets.Count() == 0)
{
// The specified worksheet does not exist.
return false;
}

string relationshipId = Sheets.First().Id.Value;
WorksheetPart worksheetPart = (WorksheetPart)myWorkbook.WorkbookPart.GetPartById(relationshipId);
SheetData sheetData = worksheetPart.Worksheet.GetFirstChild<SheetData>();

int index = 2;
foreach (var entity in GetDataToInsertInExcel())
{

Row contentRow = CreateContentRow(index, entity);
index++;
sheetData.AppendChild(contentRow);
}

workbookPart.Workbook.Save();

}

}
string[] headerColumns = new string[] { "A", "B","C","D"};
private Row CreateContentRow(int index, Bloggers objToInsert)
{

Row r = new Row ();
r.RowIndex = (UInt32) index;
int i = 0;

foreach (var prop in objToInsert.GetType().GetProperties())
{
Cell c = new Cell();
c.CellReference = headerColumns[i].ToString() + index;

if (prop.PropertyType.ToString().Equals("System.string", StringComparison.InvariantCultureIgnoreCase))
{

var result = prop.GetValue(objToInsert, null);

if (result == null)
{
result = "";
}

c.DataType = CellValues.String;
InlineString inlineString = new InlineString();
Text t = new Text();
t.Text = result.ToString();
inlineString.AppendChild(t);
c.AppendChild(inlineString);

}

if (prop.PropertyType.ToString().Equals("System.int32", StringComparison.InvariantCultureIgnoreCase))
{

var result = prop.GetValue(objToInsert, null);
if (result == null)
{
result = 0;
}

CellValue v = new CellValue();
v.Text = result.ToString();
c.AppendChild(v);

}

if (prop.PropertyType.ToString().Equals("System.boolean", StringComparison.InvariantCultureIgnoreCase))
{

var result = prop.GetValue(objToInsert, null);
if (result == null)
{
result = "False";
}
c.DataType = CellValues.InlineString;
InlineString inlineString = new InlineString();
Text t = new Text();
t.Text = result.ToString();
inlineString.AppendChild(t);
c.AppendChild(inlineString);

}


r.AppendChild(c);
i = i + 1;
}

return r;

}
private List<Bloggers> GetDataToInsertInExcel()
{
List<Bloggers> lstBloggers = new List<Bloggers>
{
new Bloggers
{
Name = "Pinal Dave",
Interest = "SQL Server",
NumberofPosts = 1500,
Speaker = true
},
new Bloggers
{
Name = "Mahesh Chand",
Interest = "C Sharp",
NumberofPosts = 1300,
Speaker = true
},
new Bloggers
{
Name = "Debug Mode",
Interest = "all",
NumberofPosts = 400,
Speaker = false
},
new Bloggers
{
Name = "Shiv Prasad Koirala",
Interest = "ASp.Net",
NumberofPosts = 500,
Speaker = true
},
new Bloggers
{
Name = "Anoop Madusudhan",
Interest = "WCF",
NumberofPosts = 500,
Speaker = false
},
};
return lstBloggers;
}

}

}

public class Bloggers
{
public string Name { get; set; }
public string Interest { get; set; }
public int NumberofPosts { get; set; }
public bool Speaker { get; set; }
}

}

Now go ahead and open Excel file and you should get the row inserted. I hope this post was useful. Thanks for reading

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“How could we fetch Excel Records using ADO.Net? Could you give me code snippet of same? “

I replied him; it is pretty possible using oledDbConnection 

I told him to add below reference

I gave him below straight forward code snippet. This function is

1. Returning DataTable
2. Reading XLS file from called YourFile.xls from F Drive.
3. Reading Sheet1

public static  DataTable  GetItemsFromExcel1()
       {

           List<Items> lstItems = new List<Items>();
           Items item;
           DataTable dt = new DataTable();

           OleDbConnection excelConnection = new OleDbConnection (@"Provider=Microsoft.Jet.OLEDB.4.0;"
                                                + @"Data Source=F:\YourFile.xls;"
                                                + @"Extended Properties=""Excel 8.0;HDR=Yes;IMEX=1;""");

           excelConnection.Open();
           try
           {
               OleDbDataAdapter dbAdapter =
                   new OleDbDataAdapter
                       ("SELECT * FROM [Sheet1$]", excelConnection);
               dbAdapter.Fill(dt);
           }
           finally
           {
               excelConnection.Close();
           }

return dt;
}

After using this function in his code , he was very happy and paid my coffee bill