How can i remove a substring from index i to first index of a or b character

int start = i;
int end = strAfterSlash.IndexOf('\\');
if (end == -1) // not found
{
  end = strAfterSlash.IndexOf(' ');
}

Str = Str.Remove(start, end);

int start = i;
int end = strAfterSlash.IndexOf('\\');
if (end == -1) // not found
{
  end = strAfterSlash.IndexOf(' ');
}

Str = Str.Remove(start, end);

Str = Str.Remove(i, (i = strAfterSlash.IndexOf('\\')) != -1 ? i : strAfterSlash.IndexOf(' '));

Str = Str.Remove(i, (i = strAfterSlash.IndexOf('\\')) != -1 ? i : strAfterSlash.IndexOf(' '));