一、DataTable简介    

          (1)构造函数 
          DataTable()   不带参数初始化DataTable 类的新实例。 
          DataTable(string tableName)  用指定的表名初始化DataTable 类的新实例。 
          DataTable(string tableName, string tableNamespace) 用指定的表名和命名空间初始化DataTable 类的新实例。 
          (2) 常用属性 
          CaseSensitive    指示表中的字符串比较是否区分大小写。 
          ChildRelations   获取此DataTable 的子关系的集合。 
          Columns             获取属于该表的列的集合。 
          Constraints        获取由该表维护的约束的集合。 
          DataSet               获取此表所属的DataSet。DataSet相关信息,可见我以前的一篇文章《数据访问(2)-DataSet》 
          DefaultView       获取可能包括筛选视图或游标位置的表的自定义视图。 
          HasErrors          获取一个值,该值指示该表所属的DataSet 的任何表的任何行中是否有错误。 
          MinimumCapacity  获取或设置该表最初的起始大小。该表中行的最初起始大小。默认值为 50。 
          Rows                  获取属于该表的行的集合。 
          TableName       获取或设置DataTable 的名称。 

          (3)常用方法 
          AcceptChanges()   提交自上次调用AcceptChanges() 以来对该表进行的所有更改。 
          BeginInit()         开始初始化在窗体上使用或由另一个组件使用的DataTable。初始化发生在运行时。

          Clear()               清除所有数据的DataTable。 
          Clone()              克隆DataTable 的结构,包括所有DataTable 架构和约束。 
          EndInit()            结束在窗体上使用或由另一个组件使用的DataTable 的初始化。初始化发生在运行时。 
          ImportRow(DataRow row)    将DataRow 复制到DataTable 中,保留任何属性设置以及初始值和当前值。 
          Merge(DataTable table)  将指定的DataTable 与当前的DataTable 合并。 
          NewRow()         创建与该表具有相同架构的新DataRow。
 
        二、DataTable使用技巧

      (1)Create a DataTable
         DataTable dt = new DataTable("Table_AX"); 

      (2)Add columns for DataTable
        //Method 1
        dt.Columns.Add("column0", System.Type.GetType("System.String"));
        //Method 2
        DataColumn dc = new DataColumn("column1", System.Type.GetType("System.Boolean"));
        dt.Columns.Add(dc); 

       (3)Add rows for DataTable
         //Initialize the row
         DataRow dr = dt.NewRow();
         dr["column0"] = "AX";
         dr["column1"] = true;
         dt.Rows.Add(dr);
         //Doesn't initialize the row
         DataRow dr1 = dt.NewRow();
         dt.Rows.Add(dr1);  

        (4)Select row
         //Search the second row 如果没有赋值,则用is null来select
         DataRow[] drs = dt.Select("column1 is null");
         DataRow[] drss = dt.Select("column0 = 'AX'"); 

        (5)Copy DataTable include data
         DataTable dtNew = dt.Copy(); 

        (6)Copy DataTable only scheme
         DataTable dtOnlyScheme = dt.Clone(); 

        (7)Operate one row
         //对dt的操作
         //Method 1
         DataRow drOperate = dt.Rows[0];
         drOperate["column0"] = "AXzhz";
         drOperate["column1"] = false;
         //Method 2
         drOperate[0] = "AXzhz";
         drOperate[1] = false;
         //Method 3
         dt.Rows[0]["column0"] = "AXzhz";
         dt.Rows[0]["column1"] = false;
         //Method 4
         dt.Rows[0][0] = "AXzhz";
         dt.Rows[0][1] = false; 

       (8)Evaluate another DataTable's row to current Datatable
         dtOnlyScheme.Rows.Add(dt.Rows[0].ItemArray); 

       (9)Convert to string
         System.IO.StringWriter sw = new System.IO.StringWriter();
         System.Xml.XmlTextWriter xw = new System.Xml.XmlTextWriter(sw);
         dt.WriteXml(xw);
         string s = sw.ToString();

        (10)Filter DataTable
         dt.DefaultView.RowFilter = "column1 <> true";
         dt.DefaultView.RowFilter = "column1 = true";

        (11)Sort row
          dt.DefaultView.Sort = "ID ,Name ASC";
          dt=dt.DefaultView.ToTable();

         (12)Bind DataTable
           //绑定的其实是DefaultView
          gvTestDataTable.DataSource = dt;
          gvTestDataTable.DataBind();

         (13)judge the DataTable’s Column name is a string
          //判断一个字符串是否为DataTable的列名
         dtInfo.Columns.Contains("AX");

         (14)DataTable convert to XML and XML convert to DataTable
          protected void Page_Load(object sender, EventArgs e)
          {
             DataTable dt_AX = new DataTable();
             //dt_AX.Columns.Add("Sex", typeof(System.Boolean));
             //DataRow dr = dt_AX.NewRow();
             //dr["Sex"] = true;
             //dt_AX.Rows.Add(dr);
             string xml=ConvertBetweenDataTableAndXML_AX(dt_AX);
             DataTable dt = ConvertBetweenDataTableAndXML_AX(xml);
         }
         public string ConvertBetweenDataTableAndXML_AX(DataTable dtNeedCoveret)
        {
             System.IO.TextWriter tw = new System.IO.StringWriter();
             //if TableName is empty, WriteXml() will throw Exception.                 

dtNeedCoveret.TableName=dtNeedCoveret.TableName.Length==0?"Table_AX":dtNeedCoveret.TableName;
             dtNeedCoveret.WriteXml(tw);
             dtNeedCoveret.WriteXmlSchema(tw);
             return tw.ToString();
        }
         public DataTable ConvertBetweenDataTableAndXML_AX(string xml)
        {
             System.IO.TextReader trDataTable = new System.IO.StringReader(xml.Substring(0, xml.IndexOf("<?xml")));
             System.IO.TextReader trSchema = new System.IO.StringReader(xml.Substring(xml.IndexOf("<?xml")));
             DataTable dtReturn = new DataTable();
             dtReturn.ReadXmlSchema(trSchema);
             dtReturn.ReadXml(trDataTable);
             return dtReturn;
        }

 以上为转载内容,原文地址http://blog.csdn.net/hcw_peter/article/details/3980723,方便一些不大了解DataTable的学习者了解下基础,本人也只是刚刚入门,希望大家多多修正和指导

下面是我做的小例子:

private void GetHourAvg()
        {
            // string dtColumnName = "";
            //string arraylistValue = "";

            TempTable();//在该方法中会获得到一个表格 DtTempHour,这个表格就是你需要的临时表
            string strtime = dtCurrent.AddDays(-1).ToString("yyyy-MM-dd") + " 12:00";//当前时间的前一天的12:00
            StartTime = Convert.ToDateTime(strtime);
            EndTime = StartTime.AddHours(1);

            for (int index = 0; index < 24; index++)//24小时循环
            {
                if (index != 0)
                {
                    StartTime = EndTime;
                    EndTime = StartTime.AddHours(1);
                }
               // MessageBox.Show(StartTime.ToString());
               // MessageBox.Show(EndTime.ToString());
                DataRow drNewRow1 = DtTemp.NewRow();//创建新行
                string name = this.dtTable.Columns[1].ToString();
                drNewRow1[name] = EndTime.ToString();//为某一列添加数据

                for (int column = 0; column < this.dtTable.Columns.Count; column++)//dtTable是你从数据库或其他地方获得的原始表格
                {
                    ArrayList arrayList = new ArrayList();//创建数组
                    for (int row = 0; row < dtTable.Rows.Count; row++)
                    {
                        string dtColumnName = this.dtTable.Rows[row][1].ToString();
                        string arraylistValue = this.dtTable.Rows[row][column].ToString();

                        DateTime dtColumn = Convert.ToDateTime(dtColumnName);

                        if (dtColumn > StartTime && dtColumn < EndTime)
                        {
                            arrayList.Add(float.Parse(arraylistValue));
                        }
                    }
                    float sum = 0;

                    foreach (float f in arrayList)
                    {
                        sum += f;
                    }
                    float avg = Convert.ToSingle(sum / arrayList.Count);
                    if (float.IsNaN(avg))
                    {
                        avg = 0;
                    }
                    drNewRow1[dtTable.Columns[column].ToString()] = avg.ToString("0.000");

                }
                DtTempHour.Rows.Add(drNewRow1.ItemArray);//将添加完数据的行加入到表中
            }  
        }临时表的好处在于所有计算在内存中完成,大大提高了运算性能,不过如果数据量过大,会使得系统性能下降.小弟菜鸟,望大家多多提意见

posted on 2012-11-18 10:09  大笨鹰  阅读(1525)  评论(0编辑  收藏  举报