DataSet的应用

Posted 2021-01-21 stanzhou47

DataSet的应用

 

一、知识描述

 

1、什么是DataSet?

DataSet为一个数据集，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，它可以单独存在，不需要一直保持和数据库的连接。

 

 

 

2、DataSet的使用方法：

（1）创建DataSet对象

DataSet ds = new DataSet();

DataSet ds = new DataSet(“DataSetName”);

（3）调用SqlDataAdapter对象的Fill方法向数据集中填充数据

SqlDataAdapter da = new SqlDataAdapter(sql, conn);

DataSet ds = new DataSet();

da.Fill(ds);

 

（4）如果DataSet中已包含数据，可以通过如下代码访问第一个表中的第i行第j列的数据（索引从0开始）

ds.Tables[0].Rows[i].ItemArray[j];

或者

ds.Tables[0].Rows.Count;

 

3、DataSet的基本结构：

 

 

二、实例代码

提取数据到树结点：

SqlConnection sqlConnection = new SqlConnection();                                              

            sqlConnection.ConnectionString =

                "Server=(local);Database=Message;Integrated Security=sspi";                     

            SqlCommand sqlCommand = new SqlCommand();                                                       

            sqlCommand.Connection = sqlConnection;                                                          

            sqlCommand.CommandText =                                                                        

                "SELECT * FROM KESHI;";                                                           

            SqlDataAdapter sqlDataAdapter = new SqlDataAdapter();                                           

            sqlDataAdapter.SelectCommand = sqlCommand;                                                      

            DataSet dataSet = new DataSet();                                                                

            sqlConnection.Open();                                                                           

            sqlDataAdapter.Fill(dataSet);                                                                   

            sqlConnection.Close();                                                                          

            DataTable keshiTable = dataSet.Tables[0];                                                  

            this.trv_keshi.Nodes.Clear();                                                           

            foreach (DataRow keshiRow in keshiTable.Rows)                                         

            {

                TreeNode keshiNode = new TreeNode();                                                   

                keshiNode.Text = keshiRow["Name"].ToString();                                     

                this.trv_keshi.Nodes.Add(keshiNode);                                                         

           }

 

 

 

提取数据到数据集：

 if (this.trv_keshi.SelectedNode.Level == 0)                                             

            {

        int KESHI = (int)this.trv_keshi.SelectedNode.Tag;                                             SqlConnection sqlConnection = new SqlConnection();                                          

        sqlConnection.ConnectionString =

            "Server=(local);Database=Message;Integrated Security=sspi";                     

           SqlCommand sqlCommand = new SqlCommand();                                                   

           sqlCommand.Connection = sqlConnection;                                                      

           sqlCommand.CommandText = "SELECT D_ID,DOCTOR FROM DMESSAGE WHERE [email protected];";                  sqlCommand.Parameters.AddWithValue("@KESHI", KESHI);                               

           SqlDataAdapter sqlDataAdapter = new SqlDataAdapter();                                       

           sqlDataAdapter.SelectCommand = sqlCommand;                                                  

           DataTable keshiTable = new DataTable();                                                  

           sqlConnection.Open();                                                                       

           sqlDataAdapter.Fill(keshiTable);                                                          

           sqlConnection.Close();                                                                      

           this.dgv_keshi.DataSource =keshiTable;                                                 

           this.dgv_keshi.Columns["D_I"].HeaderText = "工号";                                         

           this.dgv_keshi.Columns["DOCTOR"].HeaderText = "姓名";

           this.dgv_keshi.Columns[this.dgv_keshi.Columns.Count - 1].AutoSizeMode =                   

               DataGridViewAutoSizeColumnMode.Fill;

            }

三、效果截图