Three methods for generating random numbers without duplicates

The following describes three methods to generate random numbers that are not repeated:
1. implemented through the while LOOP
A random number is generated continuously through the while loop until a non-repeating number is generated. This method is easy to think of, but the efficiency is also relatively low. The instance code is as follows:
Static void Main (string [] args)
{
Int [] result = new int [10];
Int tmp =-1;
Random random = new Random ();
Bool repeat = false;
For (int I = 0; I <10; I ++)
{
Repeat = true;
While (repeat)
{
Repeat = false;

Tmp = random. Next (1, 11 );
For (int j = 0; j <I; j ++)
{
If (tmp = result [j])
{
Repeat = true;
Break;
}
}
}
Result [I] = tmp;

}

For (int I = 0; I <10; I ++)
Console. WriteLine (result [I]. ToString ());
}
2. implemented through the for Loop
Method 1 uses multiple nested loops, which is very inefficient. Therefore, I apply certain skills to reduce nested loops to improve program efficiency. The main idea is to reduce the cyclic variable by 1 if the recurrence is detected, so as to re-execute a loop and re-generate a random number until a non-repeating random number is generated. The instance code is as follows:
Static void Main (string [] args)
{
Int [] result = new int [10];
Int tmp =-1;
Random random = new Random ();
Bool repeat = false;
For (int I = 0; I <10; I ++)
{
Repeat = false;

Tmp = random. Next (1, 11 );
For (int j = 0; j <I; j ++)
{
If (tmp = result [j])
{
Repeat = true;
Break;
}
}
If (! Repeat)
{
Result [I] = tmp;
}
Else
{
I = I-1; // The cyclic variable-1
}

}

For (int I = 0; I <10; I ++)
Console. WriteLine (result [I]. ToString ());
}
This method reduces the number of nested loops and improves the efficiency!
3. Implement random sorting
This method completely subverts the basic ideas of methods 1 and 2. First, initialize an array containing numbers 1-10, and then take a random position for each loop, swap the element at this position with the element at the last position! The instance code is as follows:
Static void Main (string [] args)
{
Int [] result = new int [10];
For (int I = 0; I <10; I ++)
Result [I] = I + 1;
For (int j = 9; j> 0; j --)
{
Random r = new Random ();
Int index = r. Next (0, j );
Int temp = result [index];
Result [index] = result [j];
Result [j] = temp;
}

For (int I = 0; I <10; I ++)
Console. WriteLine (result [I]. ToString ());

}
This method eliminates loop nesting and further improves the efficiency, but it also has certain limitations. If we want to generate a random number between 5 and 10, this method of disordered order cannot be used!

Conclusion: method 1 is inefficient and is generally not recommended!
Method 2 is more common, the efficiency is higher than method 1, but the efficiency is lower than method 3
Method 3, although highly efficient, can only be applied to specific situations!

Please kindly advise!