DataTable 的用法简介

先看示例代码:

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// Put the next line into the Declarations section.

private System.Data.DataSet dataSet;

  

private void MakeDataTables()

{

    // Run all of the functions.

    MakeParentTable();

    MakeChildTable();

    MakeDataRelation();

    BindToDataGrid();

}

  

private void MakeParentTable()

{

    // Create a new DataTable.

    System.Data.DataTable table = new DataTable("ParentTable");

    // Declare variables for DataColumn and DataRow objects.

    DataColumn column;

    DataRow row;

  

    // Create new DataColumn, set DataType,

    // ColumnName and add to DataTable.   

    column = new DataColumn();

    column.DataType = System.Type.GetType("System.Int32");

    column.ColumnName = "id";

    column.ReadOnly = true;

    column.Unique = true;

    // Add the Column to the DataColumnCollection.

    table.Columns.Add(column);

  

    // Create second column.

    column = new DataColumn();

    column.DataType = System.Type.GetType("System.String");

    column.ColumnName = "ParentItem";

    column.AutoIncrement = false;

    column.Caption = "ParentItem";

    column.ReadOnly = false;

    column.Unique = false;

    // Add the column to the table.

    table.Columns.Add(column);

  

    // Make the ID column the primary key column.

    DataColumn[] PrimaryKeyColumns = new DataColumn[1];

    PrimaryKeyColumns[0] = table.Columns["id"];

    table.PrimaryKey = PrimaryKeyColumns;

  

    // Instantiate the DataSet variable.

    dataSet = new DataSet();

    // Add the new DataTable to the DataSet.

    dataSet.Tables.Add(table);

  

    // Create three new DataRow objects and add

    // them to the DataTable

    for (int i = 0; i<= 2; i++)

    {

        row = table.NewRow();

        row["id"] = i;

        row["ParentItem"] = "ParentItem " + i;

        table.Rows.Add(row);

    }

}

  

private void MakeChildTable()

{

    // Create a new DataTable.

    DataTable table = new DataTable("childTable");

    DataColumn column;

    DataRow row;

  

    // Create first column and add to the DataTable.

    column = new DataColumn();

    column.DataType= System.Type.GetType("System.Int32");

    column.ColumnName = "ChildID";

    column.AutoIncrement = true;

    column.Caption = "ID";

    column.ReadOnly = true;

    column.Unique = true;

 

    // Add the column to the DataColumnCollection.

    table.Columns.Add(column);

  

    // Create second column.

    column = new DataColumn();

    column.DataType= System.Type.GetType("System.String");

    column.ColumnName = "ChildItem";

    column.AutoIncrement = false;

    column.Caption = "ChildItem";

    column.ReadOnly = false;

    column.Unique = false;

    table.Columns.Add(column);

  

    // Create third column.

    column = new DataColumn();

    column.DataType= System.Type.GetType("System.Int32");

    column.ColumnName = "ParentID";

    column.AutoIncrement = false;

    column.Caption = "ParentID";

    column.ReadOnly = false;

    column.Unique = false;

    table.Columns.Add(column);

  

    dataSet.Tables.Add(table);

 

    // Create three sets of DataRow objects,

    // five rows each, and add to DataTable.

    for(int i = 0; i <= 4; i ++)

    {

        row = table.NewRow();

        row["childID"] = i;

        row["ChildItem"] = "Item " + i;

        row["ParentID"] = 0 ;

        table.Rows.Add(row);

    }

    for(int i = 0; i <= 4; i ++)

    {

        row = table.NewRow();

        row["childID"] = i + 5;

        row["ChildItem"] = "Item " + i;

        row["ParentID"] = 1 ;

        table.Rows.Add(row);

    }

    for(int i = 0; i <= 4; i ++)

    {

        row = table.NewRow();

        row["childID"] = i + 10;

        row["ChildItem"] = "Item " + i;

        row["ParentID"] = 2 ;

        table.Rows.Add(row);

    }

}

  

private void MakeDataRelation()

{

    // DataRelation requires two DataColumn

    // (parent and child) and a name.

    DataColumn parentColumn =

        dataSet.Tables["ParentTable"].Columns["id"];

    DataColumn childColumn =

        dataSet.Tables["ChildTable"].Columns["ParentID"];

    DataRelation relation = new

        DataRelation("parent2Child", parentColumn, childColumn);

    dataSet.Tables["ChildTable"].ParentRelations.Add(relation);

}

  

private void BindToDataGrid()

{

    // Instruct the DataGrid to bind to the DataSet, with the

    // ParentTable as the topmost DataTable.

    dataGrid1.SetDataBinding(dataSet,"ParentTable");

}

DataTable的一些属性,如:

DataTable dt = new DataTable();

dt.Columns.Add("Name",typeof(string));

//增加一列,列名为Name

DataRow dr = dt.NewRow();

dr["Name"] = "Spring Yang";

dt.Rows.Add(dr);

//增加一行;

dt.Rows.Remove(dr);

//删除一行;

dt.Cloumns.Remove("Name");

删除一列

DataTable dtnew = dt.Copy();

dtnew 指向的是dt所指向的内存地址,给dtnew操作也是对dt操作

只有这样:

DataTable dttwo = dt.Clone();

foreach(DataRow dr in dt.Rows)

{

DataRow newdr = dttwo.NewRow();

newdr.ItemArray = dr.ItemArray;

dttwo.Rows.Add(newdr);

}

再对dttwo操作就不会修改dt了.这应该是值类型和引用类型的区别吧.