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Goyo
Asked: 2020-04-22 08:01:29 +0800 CST 2020-04-22 08:01:29 +0800 CST

Concatenation in c#

  • 772

I am doing a concatenation c#where I want the result to be equal to the following:

variable = "null,null"

But I am doing this concatenation in a forand it looks more or less like this:

string variable = "";

for (int pos= 0; pos < asientos.Length; pos++)
{
    if (pos == asientos.Length - 1)
        variable += "null";
    else
        variable += "null" + ",";
}

The ifone that I place in the iteration is so that the ,(comma) is not added at the end, now the question or rather doubt is, is there a better way to do that validation in that concatenation?, and if there is, what is it? ?

c#

7 Answers

  1. Best Answer

    I recommend you to use String.Joinand thus you avoid creating the cycle forand you have a cleaner and easier to maintain code. Here I provide an example:

    using System.Linq;

//...

//asumo que asientos es un arreglo
//para el ejemplo, es de tipo int pero puede ser de cualquier tipo
int[] asientos = { 1, 2, 3 };
Console.Write(
    //String.Join permitirá unir todos los elementos de un arreglo/lista
    String.Join(
        ",", //colocamos cómo queremos que se separen los elementos
        asientos.ToList() //convertimos el arreglo en lista, si ya es una lista no necesitas aplicar este método
            .Select(x => "null") //aplicamos una conversión a los elementos para que sean "null" que es tu requerimiento
        )
    );
    • 5

  2. Hi, could you use remove , this way you would remove the last character you don't need:

    string variable = "";

for (int pos= 0; pos < asientos.Length; pos++)
{
        variable += "null" + ",";
}

variable = variable.Remove(variable.Length - 1);

    String.Remove(Int32)

    Removes all characters from a beginning to a specified position

    • 1

  3. To implement this I see two options:

    Option 1 (classic)

    var sb = new System.Text.StringBuilder();

for (int i= 0; i < asientos.Length; i++)
{
    if (i > 0)
    {
        sb.Append(",");
    }
    sb.Append("null");        
}
var variable = sb.ToString()

    The keys to this implementation are:

    • Use a System.Text.StringBuilderto concatenate the string because it is more optimal than concatenating objects stringbecause, being immutable, a memory re-allocation is performed on each concatenation
    • Adding "," to the beginning of each iteration (except for the first element) avoids repeating the string. This is especially useful when the value you are concatenating changes on each iteration.

    Option 2 (compact)

    var variable = string.Join(
    ",", 
    System.Linq.Enumerable.Repeat<string>("null", asientos.Length)
);

    The keys to this implementation are:

    • Use System.Linq.Enumerable.Repeatto create the "null" array as many times as necessary (.NET >= 4.0 required)
    • Use string.Jointo generate the final string

    These examples can be seen working in this .NET Fiddle

    I really don't know if option 1 could offer more performance but what is clear is that option 2 is much more compact

    • 1

  4. This could be a solution:

     String variable = "";

            for (int pos = 0; pos < asientos.Length;; pos++)
            {
                variable += "null" + ",";
            }
            variable = variable.Substring(0, variable.Length - 1);
            Console.Write(variable);
    • 0

  5. If the variable asientoscorresponds to a array, you should use the method Joinof the String.

    Example:

    string[] array = { "ejemplo","ejemplo2","ejemplo3" };
string palabra = String.Join(",", array);

    Now if you want the value specifically null, see that you declare a variable as int and then assign it a string, I would do it like this:

    string variable = "";
for (int pos = 0; pos < array.Length; pos++)
{
    variable += "null";
    if (pos != array.Length - 1) { variable += ","; }                                
}
    • 0

  6. Edit your question a bit on the definition of "variable" must be type String.

    I think you can use a remove()as @WilfredoP comments or substring(), for example:

    String variable = "";
string[] asientos = new string[] { "asiento Sylvia", "asient Doru", "asiento Helen" };
for (int pos= 0; pos < asientos.Length; pos++)
{    
        variable += "null" + ",";
}
variable = variable.Substring(0, variable.Length - 1);
    • 0

  7. Another option, which I think no one has mentioned would be:

    1) Concatenate all the elements of the array and a comma (except the last element).

    2) Outside the loop concatenates the last element left (no comma of course).

    The code would look like this:

    string variable = "";
for (int pos= 0; pos < asientos.Length - 1; pos++)
{
    variable += "null" + ",";
}
variable += asientos[asientos.Length - 1];
    • 0