FileStream aFile = new FileStream(SingleFile, FileMode.Open);
StreamReader sr = new StreamReader(aFile, Encoding.GetEncoding("gb2312"), true);
string FileContent = sr.ReadToEnd();
aFile.Close();
ProcessData Pd = new ProcessData();
Pd.ProceData(FileContent);

StreamReader 使用3个参数 最后一个自动检测utf-8，中文大部分是gb2312，如果不是utf-8，就用gb2312


系统自带utf 检测 ，见如下

        private void DetectEncoding()
        {
            if (this.byteLen >= 2)
            {
                this._detectEncoding = false;
                bool flag = false;
                if ((this.byteBuffer[0] == 0xfe) && (this.byteBuffer[1] == 0xff))
                {
                    this.encoding = new UnicodeEncoding(true, true);
                    this.CompressBuffer(2);
                    flag = true;
                }
                else if ((this.byteBuffer[0] == 0xff) && (this.byteBuffer[1] == 0xfe))
                {
                    if (((this.byteLen < 4) || (this.byteBuffer[2] != 0)) || (this.byteBuffer[3] != 0))
                    {
                        this.encoding = new UnicodeEncoding(false, true);
                        this.CompressBuffer(2);
                        flag = true;
                    }
                    else
                    {
                        this.encoding = new UTF32Encoding(false, true);
                        this.CompressBuffer(4);
                        flag = true;
                    }
                }
                else if (((this.byteLen >= 3) && (this.byteBuffer[0] == 0xef)) && ((this.byteBuffer[1] == 0xbb) && (this.byteBuffer[2] == 0xbf)))
                {
                    this.encoding = Encoding.UTF8;
                    this.CompressBuffer(3);
                    flag = true;
                }
                else if ((((this.byteLen >= 4) && (this.byteBuffer[0] == 0)) && ((this.byteBuffer[1] == 0) && (this.byteBuffer[2] == 0xfe))) && (this.byteBuffer[3] == 0xff))
                {
                    this.encoding = new UTF32Encoding(true, true);
                    this.CompressBuffer(4);
                    flag = true;
                }
                else if (this.byteLen == 2)
                {
                    this._detectEncoding = true;
                }
                if (flag)
                {
                    this.decoder = this.encoding.GetDecoder();
                    this._maxCharsPerBuffer = this.encoding.GetMaxCharCount(this.byteBuffer.Length);
                    this.charBuffer = new char[this._maxCharsPerBuffer];
                }
            }
        }