Kurz und bündig:
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Code:String testString = "1 / 2 / 3 / 4 /"; Boolean replace = false; for (int i = 0; i < testString.Length; i++) { if (testString[i] == '/') { if (replace) { testString = testString.Remove(i,1).Insert(i, "\r\n"); } replace = !replace; } } MessageBox.Show(testString);