标签：Nero from tostring ant connect new ddr col ons
1.思维导图
2.知识点描述
（1）介绍
DataSet可以看做是一个内存中的数据库，包括表、数据行、数据列以及表与表之间 的关系。创建一个DataSet后，它就可以单独存在，不需要一直保持和数据库的连接。应用程序需要数据时，可以直接从内存中的DataSet中读取数据。
DataSet可以包含多个表，这些表构成了数据表集合DataTableCollection，其中的每个表都是一个DataTable对象，每个表又包括数据行DataRow和列DataColumn，所有的行构成数据行集合DataRowCollection，所有的列构成数据列集合DataColumnCollection。DataSet还可以包含表与表之间的关系DataRelation。DataRelation表示数据集中DataTable之间的关系。可以用来保证执行完整性约束、数据级联。
（2）创建DataSet对象：
DataSet dataset=new DataSet();
（3）通过DataAdapter对象存储数据
SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(); sqlDataAdapter.SelectCommand = sqlCommand; DataSet dataSet = new DataSet(); sqlConnection.Open(); sqlDataAdapter.Fill(dataSet); sqlConnection.Close();
3.应用举例
树形图（使用treeview控件分级并显示数据）
（1）连接数据库
SqlConnection sqlConnection = new SqlConnection(); sqlConnection.ConnectionString = "Server=(local);Database=DB_Equipment;Integrated Security=sspi"; SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = sqlConnection; sqlCommand.CommandText= "SELECT * FROM tb_classifyone;" + "SELECT * FROM tb_classifytwo;" + "SELECT * FROM tb_classifythree;";
（2）声明并实例化数据集，用于保存查得的多张表
SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(); sqlDataAdapter.SelectCommand = sqlCommand; DataSet dataSet = new DataSet(); sqlConnection.Open(); sqlDataAdapter.Fill(dataSet); sqlConnection.Close(); DataTable classifyoneTable = dataSet.Tables[0]; DataTable classifytwoTable = dataSet.Tables[1]; DataTable classifythreeTable = dataSet.Tables[2];
（3）设置分级关系（节点）
DataRelation[] dataRelations = { new DataRelation ("classifyone_classifytwo" , classifyoneTable.Columns["No"] , classifytwoTable.Columns["ClassifyoneNo"] , false) , new DataRelation ("classifytwo_classifythree" , classifytwoTable.Columns["No"] , classifythreeTable.Columns["ClassifytwoNo"] , false) }; dataSet.Relations.AddRange(dataRelations); foreach (DataRow classifyoneRow in classifyoneTable.Rows) { TreeNode classifyoneNode = new TreeNode(); classifyoneNode.Text = classifyoneRow["Name"].ToString(); classifyoneNode.Tag = classifyoneRow["No"]; this.trv_classify.Nodes.Add(classifyoneNode); foreach (DataRow classifytwoRow in classifyoneRow.GetChildRows("classifyone_classifytwo")) { TreeNode classifytwoNode = new TreeNode(); classifytwoNode.Text = classifytwoRow["Name"].ToString(); classifytwoNode.Tag = classifytwoRow["No"]; classifyoneNode.Nodes.Add(classifytwoNode); foreach (DataRow classifythreeRow in classifytwoRow.GetChildRows("classifytwo_classifythree")) { TreeNode classifythreeNode = new TreeNode(); classifythreeNode.Text = classifythreeRow["Name"].ToString(); classifythreeNode.Tag = classifythreeRow["No"]; classifytwoNode.Nodes.Add(classifythreeNode); } } }
（4）读取数据
if (this.trv_classify.SelectedNode.Level == 2) { int ClassifythreeNo = (int)this.trv_classify.SelectedNode.Tag; SqlConnection sqlConnection = new SqlConnection(); sqlConnection.ConnectionString = "Server=(local);Database=DB_Equipment;Integrated Security=sspi"; SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = sqlConnection; sqlCommand.CommandText = "SELECT EquipmentNo,EquipmentName,Quantity FROM tb_inventory WHERE ClassifythreeNo=@ClassifythreeNo;"; sqlCommand.Parameters.AddWithValue("@ClassifythreeNo", ClassifythreeNo); SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(); sqlDataAdapter.SelectCommand = sqlCommand; DataTable inventoryTable = new DataTable(); sqlConnection.Open(); sqlDataAdapter.Fill(inventoryTable); sqlConnection.Close(); this.dgv_inventory.DataSource = inventoryTable; this.dgv_inventory.Columns[this.dgv_inventory.Columns.Count - 1].AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill; }
运行结果图
标签：Nero from tostring ant connect new ddr col ons
原文地址：https://www.cnblogs.com/JIALIH-H/p/9926145.html
