C#實值型別與參考型別(Value Type and Reference Type)

  private void button8_Click(object sender, EventArgs e)<br /> {<br /> double[][] ptArr = new double[4][];//數組乃參考型別.<br /> for (int i = 0; i < 4; i++)<br /> {<br /> ptArr[i] = new double[3];<br /> }<br /> ptArr[0][0] = 0;<br /> ptArr[0][1] = 1;<br /> ptArr[0][2] = 2;<br /> double[] d1 = new double[3];<br /> d1 = ptArr[0];<br /> //重新改變ptArr的值<br /> ptArr[0][0] = 100;<br /> ptArr[0][1] = 200;<br /> ptArr[0][2] = 300;<br /> double[] d2 = new double[3];<br /> d2 = ptArr[0];<br /> String strRes1 = null;<br /> String strRes2 = null;<br /> String strTmp = null;<br /> for (int i = 0; i < 3; i++ )<br /> {<br /> strTmp = Convert.ToString(d1[i]);<br /> strRes1 += strTmp;<br /> strRes1 += ',';<br /> }<br /> for (int i = 0; i < 3; i++)<br /> {<br /> strTmp = Convert.ToString(d2[i]);<br /> strRes2 += strTmp;<br /> strRes2 += ',';<br /> }<br /> MessageBox.Show(strRes1 + '/n' + strRes2);<br /> //結果居然顯示d1和d2的值相等!</p><p> //--><br /> //因為數組是參考型別(詳見圖),所以上述代碼中ptArr中的值的改變會影響到d1的值(d1 = ptArr[0]).<br /> //因此輸出結果均為100， 200， 300<br /> }<br /> }

 

 

 

//如若想要得到正確的結果(即:d1和d2的值不相同),應該用下面的代碼(使用數組的CopyTo()函數)

double[][] ptArr = new double[4][];<br /> for (int i = 0; i < 4; i++)<br /> {<br /> ptArr[i] = new double[3];<br /> }<br /> ptArr[0][0] = 0;<br /> ptArr[0][1] = 1;<br /> ptArr[0][2] = 2;<br /> double[] d1 = new double[3];<br /> //d1 = ptArr[0];<br /> ptArr[0].CopyTo(d1, 0);<br /> //重新改變ptArr的值<br /> ptArr[0][0] = 100;<br /> ptArr[0][1] = 200;<br /> ptArr[0][2] = 300;<br /> double[] d2 = new double[3];<br /> //d2 = ptArr[0];<br /> ptArr[0].CopyTo(d2, 0);<br /> String strRes1 = null;<br /> String strRes2 = null;<br /> String strTmp = null;<br /> for (int i = 0; i < 3; i++)<br /> {<br /> strTmp = Convert.ToString(d1[i]);<br /> strRes1 += strTmp;<br /> strRes1 += ',';<br /> }<br /> for (int i = 0; i < 3; i++)<br /> {<br /> strTmp = Convert.ToString(d2[i]);<br /> strRes2 += strTmp;<br /> strRes2 += ',';<br /> }<br /> MessageBox.Show(strRes1 + '/n' + strRes2);