Join two tables Linq example C#

C# > LINQ > Join

Join is association of objects that share a common attribute.


Example:

DataTable dtOrder = new DataTable("order");

dtOrder.Columns.Add("id", Type.GetType("System.Int32"));

dtOrder.Columns.Add("customer", Type.GetType("System.String"));

DataRow dr = dtOrder.NewRow();

dr["id"] = 1;

dr["customer"] = "X Company";

dtOrder.Rows.Add(dr);

dr = dtOrder.NewRow();

dr["id"] = 2;

dr["customer"] = "Y Company";

dtOrder.Rows.Add(dr);

DataTable dtProduct = new DataTable("product");

dtProduct.Columns.Add("order_id", Type.GetType("System.Int32"));

dtProduct.Columns.Add("product", Type.GetType("System.String"));

dr = dtProduct.NewRow();

dr["order_id"] = 1;

dr["product"] = "Product 1";

dtProduct.Rows.Add(dr);

dr = dtProduct.NewRow();

dr["order_id"] = 1;

dr["product"] = "Product 2";

dtProduct.Rows.Add(dr);

var orderProducts = from order in dtOrder.AsEnumerable()

                    join product in dtProduct.AsEnumerable() on order.Field<int>("id")                               equals product.Field<int>("order_id")

                     select new

                                {

                                    OrderId = order.Field<int>("id"),

                                    Product = product.Field<string>("product")

                                };

StringBuilder C# Example

C# > Text > StringBuilder 

StringBuilder is used when

• you want to create or modify a string without creating a new object
• increase performance when concatenating many strings together in a loop.

Example:

StringBuilder str = new StringBuilder("Product 1");

str.AppendLine(); // new line

str.Append("Product 2");

str.AppendLine();

str.AppendFormat("Total {0:C} ", 40);

textBox1.Text = str.ToString();

XElement C# Example

C# > LINQ > LINQ TO XML > XElement

XElement is an XML element.
With XElement you can create, change, delete elements.

Example

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

using System.Xml.Linq;

namespace WindowsFormsApplication9

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            XElement coTree = new XElement("Company",

                new XElement("Dept", 1),

                new XElement("Dept", 2),

                new XElement("Dept", 3));

            XElement co1Tree = new XElement("Company1",

                new XElement("CEO", 1),

                new XElement("Manager", 2),

                from el in coTree.Elements()

                    where (int)el < 3 

                        select el);

            textBox1.Text = co1Tree.ToString();

 

        }

    }

}

LINQ Enumerable Except Example

C# > LINQ > Enumerable > Except

Produces the set difference of two sequences


Example

            double[] num1 = { 1.0, 1.1 , 1.2  };
            double[] num2 = { 1.1 };

            var onlyInNum1 = num1.Except(num2);

            foreach (double number in onlyInNum1)

Determining NLS_DATE_FORMAT Oracle

Oracle > NLS_DATE_FORMAT

NLS_DATE_FORMAT specifies the default date format to use with the TO_CHAR and TO_DATE functions

Example:
Get NLS_DATE_FORMAT 

SELECT value
FROM   nls_session_parameters
WHERE  parameter = 'NLS_DATE_FORMAT'

Result:

Change and replace text line in file C#

C# > IO > File > Read/Write Lines

ReadAllLines reads all lines of the file into a string array  and closes the file.
WriteAllLines creates a new file  writes strings to the file and closes the file.

Example:

Replace text line in a file

var lines = File.ReadAllLines(Pathfile);

lines[64] = "new text";

File.WriteAllLines(Pathfile);

Remove first character from string

C# > String > Substring

Remove first character from string

myString.Substring(1)