How do i split my string in equal half and store that in variable

I'm really wondering what kind of class you may be in, or what kind of programming task in the real world, could possibly require splitting a string into two parts based on the idea of "half."

However, it's easy to do. Here's one way you could do it:

string bar = "|";
string[] splitStr = new string[] {bar};
string str = "12345678";

string[] byHalf = str.Insert(str.Length / 2, bar).Split(splitStr,StringSplitOptions.RemoveEmptyEntries);

Of course, this method is easily confused if the string you are splitting has the character you use to split it with.

Here's an example using 'StringBuilder for you to study:

string str = "12345678";
StringBuilder sb = new StringBuilder(str);
int half1 = sb.Length/2;
int half2 = sb.Length - half1;
char[] halfOne = new char[half1];
char[] halfTwo = new char[half2];
sb.CopyTo(0, halfOne, 0, half1);
sb.CopyTo(half1, halfTwo, 0, half2);
string[] results = new string[]
{
   new string(halfOne), new string(halfTwo)
};
sb.Clear();

Understand what's going on in each step of this, and you'll learn something that will be useful in the future when you are in a programming scenario where you have to deal with "heavy" string use :)

Building on @Kenneth Haugland's answer for odd strings (for you lazy folk - like me).

var value = "monobala";
var firstHalfLength = (int)(value.Length / 2);
var secondHalfLength = value.Length - firstHalfLength;
var splitPhone = new[] 
    {
        value.Substring(0, firstHalfLength),
        value.Substring(firstHalfLength, secondHalfLength)
    };