DataGrid学习六

前一示例的一个问题是，当行可编辑时，主键字段 (au_id) 也呈现为文本输入框。您不希望客户端更改该值，因为需要它来确定更新数据库中的哪一行。幸运的是，可以通过精确指定每一列相对于可编辑行的外观，禁用将此列呈现为文本框。为此需在 DataGrid 的 Columns 集合中定义每一行，使用 BoundColumn 控件分配每一列的数据字段。使用此方法，您可以完全控制列的顺序，以及它们的 ReadOnly 属性。对于 au_id 列，将 ReadOnly 属性设置为 true。当行处于编辑模式时，此列将继续呈现为标签。下面的示例说明此方法。

aspx文件里面加入DataGrid控件半设置属性，代码如下：
<body MS_POSITIONING="GridLayout">
<form id="form7" method="post" runat="server">
<asp:Literal id="Message" runat="server"></asp:Literal>
<ASP:DataGrid id="DataGrid1" runat="server" Width="800" BackColor="#ccccff" BorderColor="black" ShowFooter="false" CellPadding="3" CellSpacing="0" Font-Name="Verdana" Font-Size="8pt" HeaderStyle-BackColor="#aaaadd" OnEditCommand="MyDataGrid_Edit" OnCancelCommand="MyDataGrid_Cancel" OnUpdateCommand="MyDataGrid_Update" DataKeyField="au_id" AutoGenerateColumns="false">
<Columns>
<asp:EditCommandColumn EditText="编辑" CancelText="取消" UpdateText="更新" ItemStyle-Wrap="false" />
<asp:BoundColumn HeaderText="au_id" SortExpression="au_id" ReadOnly="True" DataField="au_id" ItemStyle-Wrap="false" />
<asp:BoundColumn HeaderText="au_lname" SortExpression="au_lname" DataField="au_lname" />
<asp:BoundColumn HeaderText="au_fname" SortExpression="au_fname" DataField="au_fname" />
<asp:BoundColumn HeaderText="phone" SortExpression="phone" DataField="phone" />
<asp:BoundColumn HeaderText="address" SortExpression="address" DataField="address" />
<asp:BoundColumn HeaderText="city" SortExpression="city" DataField="city" />
<asp:BoundColumn HeaderText="state" SortExpression="state" DataField="state" />
<asp:BoundColumn HeaderText="zip" SortExpression="zip" DataField="zip" />
<asp:BoundColumn HeaderText="contract" SortExpression="contract" DataField="contract" />
</Columns>
</ASP:DataGrid>
</form>
</body>

aspx.cs文件中加入下面代码：
导入using System.Data.SqlClient;
定义SqlConnection myConnection;
private void Page_Load(object sender, System.EventArgs e)
{
myConnection = new SqlConnection("user id=sa;password=;initial catalog=pubs;data source=jeff");
if (!IsPostBack)
  BindGrid();
}

public void MyDataGrid_Edit(Object sender, DataGridCommandEventArgs E)
{
DataGrid1.EditItemIndex = (int)E.Item.ItemIndex;
BindGrid();
}

public void MyDataGrid_Cancel(Object sender, DataGridCommandEventArgs E)
{
DataGrid1.EditItemIndex = -1;
BindGrid();
}

public void MyDataGrid_Update(Object sender, DataGridCommandEventArgs E)
{
String updateCmd = "UPDATE Authors SET au_id = @Id, au_lname = @LName, au_fname = @FName, phone = @Phone, "
+ "address = @Address, city = @City, state = @State, zip = @Zip, contract = @Contract where au_id = @Id";
SqlCommand myCommand = new SqlCommand(updateCmd, myConnection);
myCommand.Parameters.Add(new SqlParameter("@Id", SqlDbType.NVarChar, 11));
myCommand.Parameters.Add(new SqlParameter("@LName", SqlDbType.NVarChar, 40));
myCommand.Parameters.Add(new SqlParameter("@FName", SqlDbType.NVarChar, 20));
myCommand.Parameters.Add(new SqlParameter("@Phone", SqlDbType.NChar, 12));
myCommand.Parameters.Add(new SqlParameter("@Address", SqlDbType.NVarChar, 40));
myCommand.Parameters.Add(new SqlParameter("@City", SqlDbType.NVarChar, 20));
myCommand.Parameters.Add(new SqlParameter("@State", SqlDbType.NChar, 2));
myCommand.Parameters.Add(new SqlParameter("@Zip", SqlDbType.NChar, 5));
myCommand.Parameters.Add(new SqlParameter("@Contract", SqlDbType.NVarChar,1));
myCommand.Parameters["@Id"].Value = DataGrid1.DataKeys[(int)E.Item.ItemIndex];
String[] cols = {"@Id","@LName","@FName","@Phone","@Address","@City","@State","@Zip","@Contract"};
int numCols = E.Item.Cells.Count;
for (int i=2; i<numCols-1; i++) //跳过第一、第二和最后一列
{
  String colvalue =((TextBox)E.Item.Cells[i].Controls[0]).Text;
  // 检查在所需字段中是否有空值
  if (i<6 && colvalue == "")
  {
  Message.Text = "错误：“作者 ID”、“姓名”或“电话”不允许使用空值";
  return;
  }
  myCommand.Parameters[cols[i-1]].Value = colvalue;
}

//追加最后一行，将 true/false 值转换为 0/1
if (String.Compare(((TextBox)E.Item.Cells[numCols-1].Controls[0]).Text, "True", true)==0)
  myCommand.Parameters["@Contract"].Value =  "1";
else
  myCommand.Parameters["@Contract"].Value =  "0";
myCommand.Connection.Open();
try
{
  myCommand.ExecuteNonQuery();
  Message.Text = "<b>已更新记录</b><br>" + updateCmd;
  DataGrid1.EditItemIndex = -1;
}
catch (SqlException e)
{
  if (e.Number == 2627)
   Message.Text = "错误：已存在具有相同主键的记录";
  else
   Message.Text = "错误：未能更新记录，请确保正确填写了字段";
}

myCommand.Connection.Close();
BindGrid();
}
public void BindGrid()
{
SqlDataAdapter myCommand = new SqlDataAdapter("select * from Authors", myConnection);
DataSet ds = new DataSet();
myCommand.Fill(ds, "Authors");
DataGrid1.DataSource=ds.Tables["Authors"].DefaultView;
DataGrid1.DataBind();
}

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