一次性记录插入然后更新很多次

Question

我有一个表单，用户可以插入，查看和更新​​数据。数据插入只完成一次，然后更新可以进行多次。默认情况下，用户将能够查看数据是否存在于数据库中。

我试过这个，但它没有插入数据库。然后假设数据库中存在数据，并且当用户想要更新记录时，它会抛出一个错误 - DataReader已打开。

private void display_Emp() 
    { 
     try 
     { 
      using (sqlCon = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString)) 
      { 
       sqlCon.Open(); 

       SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Employee", sqlCon); 
       DataSet ds = new DataSet("Employee"); 
       da.Fill(ds, "Employee"); 
       int x = 0; 
       for (x = 0; x < ds.Tables[0].Rows.Count; x++) 
       { 
        txtID.Text = ds.Tables[0].Rows[x][1].ToString(); 
        txtEmpName.Text = ds.Tables[0].Rows[x][2].ToString(); 
       } 
      } 
     } 
     catch(Exception exx) { 
      MessageBox.Show(exx.Message); 
     } 
     finally { 
      sqlCon.Close(); 
     } 
    } 

private void btnSave_Click(object sender, EventArgs e) 
{ 
    try 
    { 
     using (sqlCon = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString)) 
     { 
      sqlCon.Open(); 
      SqlCommand com = new SqlCommand("SELECT * FROM Employee", sqlCon); 

      read = com.ExecuteReader(); 

      while (read.Read()) 
      {      
       if (read.HasRows) 
       { 
        SqlCommand update = new SqlCommand("UPDATE Employee SET EmpID = '" + txtID.Text + "' , EmpName = '" + txtEmpName.Text + "', sqlCon); 
        update.ExecuteNonQuery(); 
        MessageBox.Show("Employee details updated!", "Employee", MessageBoxButtons.OK, MessageBoxIcon.Information); 
       } 
       else 
       { 
        SqlCommand comm = new SqlCommand("INSERT INTO Employee(EmpID, EmpName) VALUES ('" + txtID.Text + "','" + txtEmpName.Text + "')", sqlCon); 
        comm.ExecuteNonQuery(); 
        MessageBox.Show("Employee details saved!", "Employee", MessageBoxButtons.OK, MessageBoxIcon.Information); 
       } 
      } 
     } 
    } 
    catch(Exception ex) 
    { 
     MessageBox.Show(ex.Message); 
    } 
    finally 
    { 
     read.Close(); 
     sqlCon.Close(); 
    }     
} 

编辑：

表： - Deepz（ID INT PK，Goodname VARCHAR（50））

DECLARE @ID int 
DECLARE @Goodname varchar(50) 

    MERGE Deepz t 
    USING (SELECT @ID[ID], @Goodname[Goodname]) s 
     ON (t.ID = s.ID) 
    WHEN MATCHED THEN 
     UPDATE 
     SET t.Goodname = @Goodname 
    WHEN NOT MATCHED THEN 
     INSERT (ID, Goodname) 
     VALUES (@ID, @Goodname); 

错误：

Msg 102, Level 15, State 1, Line 1 
Incorrect syntax near 't'. 
Msg 137, Level 15, State 2, Line 2 
Must declare the scalar variable "@ID". 

Answer 1

你应该改变你将功能保存到：

• 如果你的SQL Server 2008或更高版本上，使用SQL Merge语句来插入或更新取决于是否存在记录或不

 
    DECLARE @nameField VarChar(50) = 'some data' 

    MERGE dbo.MyTable t 
    USING (SELECT @nameField [field]) s 
     ON t.myData = s.field 
    WHEN MATCHED THEN 
     UPDATE 
     SET t.myData = @nameField 
    WHEN NOT MATCHED THEN 
     INSERT (myData) 
     VALUES (@nameField); 

• 如果你的SQL Server 2005或更早上，你需要使用类似于下面的东西，但是你可能会遇到竞争状况（但是imho仍然会比你原来的设计更好，这也有可能导致竞争状况），所以根据你的环境，你可能需要四处游玩带锁等

 
    IF EXISTS (SELECT * FROM Deepz WHERE [ID] = @ID) 
    BEGIN 
     UPDATE Deepz 
     SET Goodname = @Goodname 
     WHERE [ID] = @ID 
    END 
    ELSE 
    BEGIN 
     INSERT Deepz (ID, Goodname) 
     VALUES (@ID, @Goodname); 
    END 

• 使用SQL PARAMS，而不是通过级联构建的声明，将节省您从SQL injection攻击

 
    UPDATE Employee SET EmpID = @id, EmpName = @name 

然后

 
    SqlCommand comm = new SqlCommand(...); 
    // note below is a bit simplified, in reality you should do int.TryParse 
    comm.Parameters.Add(@id, SqlDbType.Int).Value = int.Parse(txtID.Text); 

Answer 2

这是一个有点拍摄黑暗但是，试试这个：

private void btnSave_Click(object sender, EventArgs e) 
{ 
    try 
    { 
     using (sqlCon = new SqlConnection(ConfigurationManager.ConnectionStrings["Connection"].ConnectionString)) 
     { 
     sqlCon.Open(); 
     SqlCommand com = new SqlCommand("SELECT * FROM Employee", sqlCon); 
     com.Parameters.AddWithValue(@empID, SqlDbType.Int).Value = int.Parse(txtID.Text); // Add this line 
     com.Parameters.AddWithValue(@empName, SqlDbType.NVarChar).Value = txtEmpName.Text; // Add this line too 
     SqlDataReader read = new SqlDataReader(); // You also need to 'new' up your SqlDataReader. 
     read = com.ExecuteReader(); 

     while (read.Read()) 
     {      
      if (read.HasRows) 
      { 
      SqlCommand update = new SqlCommand("UPDATE Employee SET EmpID = @empID, EmpName = @empName", sqlCon); 
      update.ExecuteNonQuery(); 
      MessageBox.Show("Employee details updated!", "Employee", MessageBoxButtons.OK, MessageBoxIcon.Information); 
      } 

      else 
      { 
       SqlCommand comm = new SqlCommand("INSERT INTO Employee(EmpID, EmpName) VALUES (@empID, @empName)", sqlCon); 
       comm.ExecuteNonQuery(); 
       MessageBox.Show("Employee details saved!", "Employee", MessageBoxButtons.OK, MessageBoxIcon.Information); 
      } 
     } 
    } 

    catch(Exception ex) 
    { 
     MessageBox.Show(ex.Message); 
    } 

    finally 
    { 
     read.Close(); 
     sqlCon.Close(); 
    } 
} 

Answer 3

从例子中我看到“If”条件和“While”条件看起来像倒过来。

http://msdn.microsoft.com/en-us/library/haa3afyz%28v=vs.80%29.aspx

您检查，看看是否先有行，然后使用`datareader`和相同的连接`ExecuteNonQuery`不工作对他们