How can i split the string only once using C#

Specify the maximum number of items that you want:

string[] splitted = text.Split(" - ", count: 2, StringSplitOptions.None);

string s = "a - b - c";
string[] parts = s.Split('-', count: 2);
// note, you'll still need to trim off any whitespace

"a-b-c".Split( new char[] { '-' }, 2 );

You could use indexOf() to find the first instance of the character you want to split with, then substring() to get the two aspects. For example...

int pos = myString.IndexOf('-');
string first = myString.Substring(0, pos);
string second = myString.Substring(pos);

This is a rough example - you'll need to play with it if you don't want the separator character in there - but you should get the idea from this.

string[] splitted = "a - b - c".Split(new char[]{' ', '-'}, 2, StringSplitOptions.RemoveEmptyEntries);

var str = "a-b-c";
int splitPos = str.IndexOf('-');
string[] split = { str.Remove(splitPos), str.Substring(splitPos + 1) };

I have joined late and many of above answers are matched with my following words:

string has its own

Split

You can use the same to find the solution of your problem, following is the example as per your issue:

using System;

public class Program
{
    public static void Main()
    {
        var PrimaryString = "a - b - c";
        var strPrimary  = PrimaryString.Split( new char[] { '-' }, 2 );
        Console.WriteLine("First:{0}, Second:{1}",strPrimary[0],strPrimary[1]);

    }
}

Output:
First:a , Second: b - c