Category Archives: C#

C# programming with CSharp

Security – PVS‑Studio.

The development team comes with this intro: PVS‑Studio is a static analyzer on guard of code quality, security known ad SAST, and code safety. PVS‑Studio detects various errors – typos, dead code, and potential vulnerabilities (Static Application Security Testing, SAST). The analyzer matches warnings to the Common Weakness Enumeration, SEI CERT Coding Standards, and supports… Read More »

C# – First steps with C# and .NET – part 049.

In the last tutorial, I solve the connection with the firebase database. In this tutorial, I add a new record into the database and I fix the source code to work well with this. See the source code:

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        protected override void OnCreate(Bundle savedInstanceState)
        {
 
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.activity_main);
          
            button = FindViewById<Button>(Resource.Id.button1);
            this.FindViewById<Button>(Resource.Id.button1).Click += this.Button_Clicked;
        }
 
        void Button_Clicked(System.Object sender, System.EventArgs e) {
 
            mytextView = FindViewById<TextView>(Resource.Id.textView1);
            this.FindViewById<TextView>(Resource.Id.textView1).Text = "Is set!";
            recordData = FindViewById<EditText>(Resource.Id.editText1);
            string conn = "https://xamarinapp-8cccb-default-rtdb.europe-west1.firebasedatabase.app";
            FirebaseClient firebaseClient = new Firebase.Database.FirebaseClient(conn);
            firebaseClient.Child("Records").PostAsync(new MyDatabaseRecord
            {
                MyProperty = recordData.Text
            });
            recordData.Text = "";
        }

You can see the result of this source code into the emulator software and the web… Read More »

C# – First steps with C# and .NET – part 048.

Today’s tutorial is about C# and the google firebase service. The main goal is to connect a Xamarin Application with an Firebase Database. You need to create a simple database without any records on this. Open your Firebase account and create a database , you will see the URL of this database like this:

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https://xamarinapp-YOUR_DATABASE.firebasedatabase.app/

… Read More »

C# – First steps with C# and .NET – part 047.

Extension methods enable you to “add” methods to existing types without creating a new derived type, recompiling, or otherwise modifying the original type. Extension methods are static methods, but they’re called as if they were instance methods on the extended type. see the official website. Let’s see one simple example:

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using System;
using System.Linq;
using System.Collections.Generic;
 
public static class ExtensionMethods
{
//public static IEnumerable<T> Filter<T>(this IEnumerable<string> myArray)
//public static int[] Filter(this IEnumerable<string> someArray)
public static IEnumerable<int> Filter(this IEnumerable<string> someArray, Func<int,bool> func)
{
return someArray.Select(i => Convert.ToInt32(i)).Where(i => func(i));
}
}
 
public class Program
{
public static void Main()
{
// https://www.youtube.com/watch?v=v_cgQzp8YHQ
Console.WriteLine("Hello World");
/*
Extension methods let us add methods to existing types without creating a new  derivated type
*/
var myArray = new int[] {1,2,3,4,5,6,7,8,9};
// Where is a extension method
var evenNumbers1 = myArray.Where(x => x % 2 == 0);
Console.WriteLine($"Even numbers1 are : {string.Join(',' , evenNumbers1)}");
var evenNumbers2 = myArray.Select(x => $"Item number : {x}");
Console.WriteLine($"Even numbers2 are : {string.Join(',' , evenNumbers2)}");
// use an class extension method
var myArrayString = new string[] {"1","2","3"};
var evenNumbers3 = myArrayString.Filter(x => x > 1).Select(x => $"Item number: {x}");
Console.WriteLine($"Even numbers3 are : {string.Join(',' , evenNumbers3)}");
}
}

In this example, you… Read More »

C# – First steps with C# and .NET – part 045.

In this tutorial, I will show you how you can multiply two matrices using the C# programming language. The full source code in C# can be found on my account on dotnetfiddle online tool. This is the source code I used:

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using System;
using System.Collections.Generic;
public class Program
{
public static void Main()
{
Console.WriteLine("Hello World");
 
int i,j,k;
int[,] A = {{1, 2}, {3, 5}, {1,1976}};
int[,] B = {{5, 10, 5}, {100, 1000, 1}};
var ARows = A.GetLength(0);  
var ACols = A.GetLength(1);  
var BRows = B.GetLength(0);  
var BCols = B.GetLength(1);
Console.WriteLine("Numebr of rows in matrix A:  " + ARows + " and number of columns in matrix A: " + ACols);
Console.WriteLine("Numebr of rows in matrix B:  " + BRows + " and number of columns in matrix B: " + BCols);
int[,] C = new int[ARows, BRows];
 
List<int> matrixDimA = new List<int>();
List<int> matrixDimB = new List<int>();
Console.WriteLine("Number of matrix A elements are :" + ARows *ACols);  
//matrixDimA.Reverse();
Console.WriteLine("Elements of matrix A elements are :");  
for (i = 0; i < ARows; i++)
{
Console.Write("[");
for (j = 0; j < ACols; j++)
{
if (j != ACols - 1)
{
Console.Write( A[i, j] + ",");
}
else
{
Console.Write( A[i, j]);
}
}
Console.WriteLine("]");
}
Console.WriteLine("Number of matrix A elements are :" + BRows *BCols);  
Console.WriteLine("Elements of matrix A elements are :");  
for (i = 0; i < BRows; i++)
{
Console.Write("[");
for (j = 0; j < BCols; j++)
{
if (j != BCols - 1)
{
Console.Write( B[i, j] + ",");
}
else
{
Console.Write( B[i, j]);
}
}
Console.WriteLine("]");
}
 
if((ARows == BCols) & (ACols == BRows))
{
Console.WriteLine("Matrix multiplication is possible because: ");
Console.WriteLine("Numebr of rows in matrix A:  " + ARows + " = with number of columns in matrix B: " + BCols);
Console.WriteLine("Numebr of columns in matrix A:  " + ACols + " = with number of rows in matrix B: " + BRows);
for (i = 0; i < ARows; i++)
{
Console.Write("[");
for (j = 0; j < BRows; j++)
{
if (j != ACols - 1)
{
C[i, j] = A[i, j] * B[j, i];
Console.Write( C[i, j] + ",");
}
else
{
C[i, j] = A[i, j] * B[j, i];
Console.Write( C[i, j]);
}
}
Console.WriteLine("]");
}
 
} else {
Console.WriteLine("Matrix multiplication rows is not possible.");
}
var CRows = C.GetLength(0);  
var CCols = C.GetLength(1);
Console.WriteLine("Number of matrix C elements are :" + CRows *CCols);  
Console.WriteLine("Elements of matrix C elements are :");  
 
for (i = 0; i < CRows; i++)
{
Console.Write("[");
for (j = 0; j < CCols; j++)
{
if (j != CCols - 1)
{
Console.Write( C[i, j] + ",");
}
else
{
Console.Write( C[i, j]);
}
}
Console.WriteLine("]");
}
}
}

This is the output:

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Hello World
Numebr of rows in matrix A:  3 and number of columns in matrix A: 2
Numebr of rows in matrix B:  2 and number of columns in matrix B: 3
Number of matrix A elements are :6
Elements of matrix A elements are :
[1,2]
[3,5]
[1,1976]
Number of matrix A elements are :6
Elements of matrix A elements are :
[5,10,5]
[100,1000,1]
Matrix multiplication is possible because:
Numebr of rows in matrix A:  3 = with number of columns in matrix B: 3
Numebr of columns in matrix A:  2 = with number of rows in matrix B: 2
[5,200]
[30,5000]
[5,1976]
Number of matrix C elements are :6
Elements of matrix C elements are :
[5,200]
[30,5000]
[5,1976]