10进制转26进制作为Excel列名

       [Test]
        public void Test10To26()
        {
            Assert.AreEqual("A", GetColumnName(1));
            Assert.AreEqual("B", GetColumnName(2));
            Assert.AreEqual("Z", GetColumnName(26));
            Assert.AreEqual("ZZ", GetColumnName(26*26 + 26));
            Assert.AreEqual("ZZZ", GetColumnName(26 * 26 * 26 + 26 * 26 + 26));
            Assert.AreEqual("AA", GetColumnName(27));
            Assert.AreEqual("AB", GetColumnName(28));
            Assert.AreEqual("AC", GetColumnName(29));

            int aaa = 1 * 26 * 26 + 1 * 26 + 1; //AAA;
            Assert.AreEqual("AAA", GetColumnName(aaa));

            int aab = 1 * 26 * 26 + 1 * 26 + 2;
            Assert.AreEqual("AAB", GetColumnName(aab));

            int bbb = 2 * 26 * 26 + 2 * 26 + 2; //AAA;
            Assert.AreEqual("BBB", GetColumnName(bbb));
        }
      
        public string GetColumnName(int intValue)
        {
            string result = "";
            if (intValue <= 26)
            {
                result = (char)(intValue + 96) + result;
                return result.ToUpper();
            }
           

            int modOf26 = intValue % 26;

            int left = 0;

            if (modOf26 == 0)
            {
                result = 'Z' + result;
                left =  intValue - 26;
            }
            else
            {
                result = (char)(modOf26 + 96) + result;
                left = intValue - modOf26;
            }



            int nextInputValue = left / 26;

            if (nextInputValue == 0)
                return result.ToUpper();

            if (nextInputValue > 26)
                result = GetColumnName(nextInputValue) + result;
            else
                result = (char)(nextInputValue + 96) + result;

            return result.ToUpper();
         
        }