C＃字符串对比，并且取出其中不同的字符串

如题：
ｓｔｒｉｎｇ　ｓｔｒ１＝＂１２３４５６＂；
ｓｔｒｉｎｇ　ｓｔｒ２＝＂１２３ａｂｃ４５ｅｆ６ｇｈｉ＂；
如何得到ｓｔｒ２的ａｂｃ，ｅｆ，ｇｈｉ．

大概写了个js，C#题主可以按照js代码形式改下，逻辑差不多

<style>
    .editor {
        border: solid 1px #ccc;
        width: 200px;
        height: 100px;
        margin-right: 10px;
        padding: 10px;
        display: inline-block;
        vertical-align: top;float:left
    }
</style>
<div class="editor" contenteditable="true"></div>
<div class="editor" contenteditable="true"></div>

<input type="button" value="找不同" onclick="findDiff()" />
<script>
    function getDiff(str1, str2) {
        var diffs = [], s = str1.charAt(0), t = s, index1, index2, diff
        index1 = str2.indexOf(s);
        if (index1 == -1) return [{ diff: str2}];
        for (var i = 1; i < str1.length; i++) {
            var c = str1.charAt(i)
            t += c;
            index2 = str2.indexOf(t);
            if (index1 == index2) { s += c; }
            else {
                if (index1 == 0) {
                    diffs.push({ diff: s, match: 1 });
                    index2 = str2.indexOf(c);
                    if (index2 != -1) {
                        diff = str2.substring(s.length, index2)
                        diffs.push({ diff});

                    }
                    else {
                        diff = str2.substring(s.length);
                        diffs.push({ diff});
                        break;
                    }
                    str2 = str2.substring(s.length + diff.length);
                    index1 = index2 = str2.indexOf(c)
                    t = s = c;
                }
                else {
                    diff = str2.substring(0, index1);
                    diffs.push({ diff });
                    diffs.push({ diff: s, match: 1 });

                    str2 = str2.substring(index1 + s.length)

                    t = c;
                    index2 = str2.indexOf(t);
                    if (index2 == -1) {//剩余字符不包含代查找字符
                        diff = str2;
                        diffs.push({ diff });
                        break;
                    }
                    index1 = index2;
                    s = t;
                }
            }
        }
        diff = str2.substring(s.length)
        if (diff) {
            diffs.push({ diff: s, match: 1 });
            diffs.push({ diff })
        }
        return diffs
    }
    function findDiff() {
        var e = document.querySelectorAll('.editor');
        var str1 = e[0].innerText.trim(), str2 = e[1].innerText.trim();
        if (str1 && str2) {
            var diffs = getDiff(str1, str2);
            console.log(diffs)
            e[1].innerHTML = diffs.map(i => i.match ? i.diff : `<font color=red>${i.diff}</font>`).join('')
        }
    }
</script>

如图显示的效果，有大神知道的吗

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