FormParameter.FormField Propriedade
Definição
Obtém ou define o nome da variável de formulário ao qual o parâmetro está associado.Gets or sets the name of the form variable that the parameter binds to.
public:
property System::String ^ FormField { System::String ^ get(); void set(System::String ^ value); };
public string FormField { get; set; }
member this.FormField : string with get, set
Public Property FormField As String
Valor da propriedade
Uma cadeia de caracteres que identifica a variável de formulário à qual o parâmetro está associado.A string that identifies the form variable to which the parameter binds.
Exemplos
O exemplo de código a seguir demonstra como exibir dados filtrados usando um ObjectDataSource controle e um FormParameter para recuperar dados de um objeto comercial de camada intermediária e um GridView controle para exibir os resultados.The following code example demonstrates how to display filtered data using an ObjectDataSource control and a FormParameter to retrieve data from a middle-tier business object and a GridView control to display the results.
O exemplo de código consiste em um TextBox , um GridView controle, o ObjectDataSource controle e um botão de envio.The code example consists of a TextBox, a GridView control, the ObjectDataSource control, and a submit button. Por padrão, o TextBox é preenchido com o nome de um dos funcionários da Northwind Traders.By default, the TextBox is populated with the name of one of the Northwind Traders employees. O GridView exibe informações sobre o funcionário identificado pelo nome no TextBox .The GridView displays information about the employee identified by the name in the TextBox. Para recuperar dados em outro funcionário, insira o nome completo do funcionário no TextBox e clique no botão.To retrieve data on another employee, enter the full name of the employee in the TextBox and click the button.
A FilterExpression propriedade especifica uma expressão usada para filtrar os dados recuperados pelo SelectMethod .The FilterExpression property specifies an expression used to filter the data retrieved by the SelectMethod. Essa propriedade usa espaços reservados de parâmetro que são avaliados para os parâmetros contidos na FilterParameters coleção.This property uses parameter placeholders that are evaluated to the parameters contained in the FilterParameters collection. Neste exemplo, o espaço reservado de parâmetro é um FormParameter associado ao valor do TextBox controle.In this example, the parameter placeholder is a FormParameter bound to the value of the TextBox control.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS" Assembly="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void ObjectDataSource1_Filtering(object sender, ObjectDataSourceFilteringEventArgs e)
{
if (Textbox1.Text == "")
{
e.ParameterValues.Clear();
e.ParameterValues.Add("FullName", "Nancy Davolio");
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>ObjectDataSource - C# Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<p>Show all users with the following name.</p>
<asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />
<asp:gridview
id="GridView1"
runat="server"
datasourceid="ObjectDataSource1"
autogeneratecolumns="False">
<columns>
<asp:boundfield headertext="ID" datafield="EmpID" />
<asp:boundfield headertext="Name" datafield="FullName" />
<asp:boundfield headertext="Street Address" datafield="Address" />
</columns>
</asp:gridview>
<!-- Security Note: The ObjectDataSource uses a FormParameter,
Security Note: which does not perform validation of input from the client. -->
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployeesAsDataSet"
typename="Samples.AspNet.CS.EmployeeLogic"
filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
<filterparameters>
<asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
</filterparameters>
</asp:objectdatasource>
<p><asp:button id="Button1" runat="server" text="Search" /></p>
</form>
</body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB" Assembly="Samples.AspNet.VB" %>
<%@ Page language="vb" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub ObjectDataSource1_Filtering(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.ObjectDataSourceFilteringEventArgs)
If Textbox1.Text = "" Then
e.ParameterValues.Clear()
e.ParameterValues.Add("FullName", "Nancy Davolio")
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>ObjectDataSource - VB Example</title>
</head>
<body>
<form id="Form1" method="post" runat="server">
<p>Show all users with the following name.</p>
<asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />
<asp:gridview
id="GridView1"
runat="server"
datasourceid="ObjectDataSource1"
autogeneratecolumns="False">
<columns>
<asp:boundfield headertext="ID" datafield="EmpID" />
<asp:boundfield headertext="Name" datafield="FullName" />
<asp:boundfield headertext="Street Address" datafield="Address" />
</columns>
</asp:gridview>
<!-- Security Note: The ObjectDataSource uses a FormParameter,
Security Note: which does not perform validation of input from the client. -->
<asp:objectdatasource
id="ObjectDataSource1"
runat="server"
selectmethod="GetAllEmployeesAsDataSet"
typename="Samples.AspNet.VB.EmployeeLogic"
filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
<filterparameters>
<asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
</filterparameters>
</asp:objectdatasource>
<p><asp:button id="Button1" runat="server" text="Search" /></p>
</form>
</body>
</html>
O exemplo de código a seguir mostra o objeto comercial de camada intermediária que o exemplo de código anterior usa.The following code example shows the middle-tier business object that the previous code example uses. Este exemplo consiste em duas classes básicas: a EmployeeLogic classe encapsula a lógica de negócios e a NorthwindEmployee classe é uma classe de modelo que contém apenas a funcionalidade básica necessária para carregar e manter dados da camada de dados.This example consists of two basic classes: The EmployeeLogic class encapsulates business logic, and the NorthwindEmployee class is a model class that contains only the basic functionality required to load and persist data from the data tier. Para simplificar, a EmployeeLogic classe cria um conjunto estático de dados, em vez de recuperar os dados de uma camada de dados.For simplicity, the EmployeeLogic class creates a static set of data, rather than retrieving the data from a data tier. Ele também é útil para este exemplo, porque o exemplo depende do usuário para fornecer o nome completo de um funcionário da Northwind Traders para demonstrar a filtragem.It is also helpful for this example, because the sample relies on the user to provide the full name of a Northwind Traders employee to demonstrate filtering. Para obter um exemplo funcional completo, você deve compilar e usar essas classes com os exemplos de código ASP.NET fornecidos.For a complete working example, you must compile and use these classes with the ASP.NET code examples provided.
Importante
O FormParameter não valida o valor passado pelo elemento form de qualquer forma; ele usa o valor bruto.The FormParameter does not validate the value passed by the form element in any way; it uses the raw value. Na maioria dos casos, você pode validar o valor de FormParameter antes que ele seja usado por um controle da fonte de dados manipulando um evento, como o Selecting evento,, Updating Inserting ou Deleting exposto pelo controle da fonte de dados que você está usando.In most cases, you can validate the value of the FormParameter before it is used by a data source control by handling an event, such as the Selecting, Updating, Inserting, or Deleting event exposed by the data source control you are using. Se o valor do parâmetro não passar nos testes de validação, você poderá cancelar a operação de dados definindo a Cancel propriedade da CancelEventArgs classe associada como true .If the value of the parameter does not pass your validation tests, you can cancel the data operation by setting the Cancel property of the associated CancelEventArgs class to true.
namespace Samples.AspNet.CS {
using System;
using System.Collections;
using System.Data;
using System.Web.UI.WebControls;
//
// EmployeeLogic is a stateless business object that encapsulates
// the operations you can perform on a NorthwindEmployee object.
//
public class EmployeeLogic {
// Returns a collection of NorthwindEmployee objects.
public static ICollection GetAllEmployees () {
ArrayList data = new ArrayList();
data.Add(new NorthwindEmployee(1,"Nancy","Davolio","507 - 20th Ave. E. Apt. 2A"));
data.Add(new NorthwindEmployee(2,"Andrew","Fuller","908 W. Capital Way"));
data.Add(new NorthwindEmployee(3,"Janet","Leverling","722 Moss Bay Blvd."));
data.Add(new NorthwindEmployee(4,"Margaret","Peacock","4110 Old Redmond Rd."));
data.Add(new NorthwindEmployee(5,"Steven","Buchanan","14 Garrett Hill"));
data.Add(new NorthwindEmployee(6,"Michael","Suyama","Coventry House Miner Rd."));
data.Add(new NorthwindEmployee(7,"Robert","King","Edgeham Hollow Winchester Way"));
return data;
}
public static NorthwindEmployee GetEmployee(object anID) {
ArrayList data = GetAllEmployees() as ArrayList;
int empID = Int32.Parse(anID.ToString());
return data[empID] as NorthwindEmployee;
}
//
// To support basic filtering, the employees cannot
// be returned as an array of objects, rather as a
// DataSet of the raw data values.
public static DataSet GetAllEmployeesAsDataSet () {
ICollection employees = GetAllEmployees();
DataSet ds = new DataSet("Table");
// Create the schema of the DataTable.
DataTable dt = new DataTable();
DataColumn dc;
dc = new DataColumn("EmpID", typeof(int)); dt.Columns.Add(dc);
dc = new DataColumn("FullName",typeof(string)); dt.Columns.Add(dc);
dc = new DataColumn("Address", typeof(string)); dt.Columns.Add(dc);
// Add rows to the DataTable.
DataRow row;
foreach (NorthwindEmployee ne in employees) {
row = dt.NewRow();
row["EmpID"] = ne.EmpID;
row["FullName"] = ne.FullName;
row["Address"] = ne.Address;
dt.Rows.Add(row);
}
// Add the complete DataTable to the DataSet.
ds.Tables.Add(dt);
return ds;
}
}
public class NorthwindEmployee {
public NorthwindEmployee (int anID,
string aFirstName,
string aLastName,
string anAddress) {
ID = anID;
firstName = aFirstName;
lastName = aLastName;
address = anAddress;
}
private object ID;
public string EmpID {
get { return ID.ToString(); }
}
private string lastName;
public string LastName {
get { return lastName; }
set { lastName = value; }
}
private string firstName;
public string FirstName {
get { return firstName; }
set { firstName = value; }
}
public string FullName {
get { return FirstName + " " + LastName; }
}
private string address;
public string Address {
get { return address; }
set { address = value; }
}
}
}
Imports System.Collections
Imports System.Data
Imports System.Web.UI.WebControls
Namespace Samples.AspNet.VB
'
' EmployeeLogic is a stateless business object that encapsulates
' the operations you can perform on a NorthwindEmployee object.
'
Public Class EmployeeLogic
' Returns a collection of NorthwindEmployee objects.
Public Shared Function GetAllEmployees() As ICollection
Dim data As New ArrayList()
data.Add(New NorthwindEmployee(1, "Nancy", "Davolio", "507 - 20th Ave. E. Apt. 2A"))
data.Add(New NorthwindEmployee(2, "Andrew", "Fuller", "908 W. Capital Way"))
data.Add(New NorthwindEmployee(3, "Janet", "Leverling", "722 Moss Bay Blvd."))
data.Add(New NorthwindEmployee(4, "Margaret", "Peacock", "4110 Old Redmond Rd."))
data.Add(New NorthwindEmployee(5, "Steven", "Buchanan", "14 Garrett Hill"))
data.Add(New NorthwindEmployee(6, "Michael", "Suyama", "Coventry House Miner Rd."))
data.Add(New NorthwindEmployee(7, "Robert", "King", "Edgeham Hollow Winchester Way"))
Return data
End Function 'GetAllEmployees
Public Shared Function GetEmployee(anID As Object) As NorthwindEmployee
Dim data As ArrayList = CType(GetAllEmployees(), ArrayList)
Dim empID As Integer = Int32.Parse(anID.ToString())
Return CType(data(empID),NorthwindEmployee)
End Function 'GetEmployee
' To support basic filtering, the employees cannot
' be returned as an array of objects, rather as a
' DataSet of the raw data values.
Public Shared Function GetAllEmployeesAsDataSet() As DataSet
Dim employees As ICollection = GetAllEmployees()
Dim ds As New DataSet("Table")
' Create the schema of the DataTable.
Dim dt As New DataTable()
Dim dc As DataColumn
dc = New DataColumn("EmpID", GetType(Integer))
dt.Columns.Add(dc)
dc = New DataColumn("FullName", GetType(String))
dt.Columns.Add(dc)
dc = New DataColumn("Address", GetType(String))
dt.Columns.Add(dc)
' Add rows to the DataTable.
Dim row As DataRow
Dim ne As NorthwindEmployee
For Each ne In employees
row = dt.NewRow()
row("EmpID") = ne.EmpID
row("FullName") = ne.FullName
row("Address") = ne.Address
dt.Rows.Add(row)
Next
' Add the complete DataTable to the DataSet.
ds.Tables.Add(dt)
Return ds
End Function 'GetAllEmployeesAsDataSet
End Class
Public Class NorthwindEmployee
Public Sub New(anID As Integer, aFirstName As String, aLastName As String, anAddress As String)
ID = anID
Me.aFirstName = aFirstName
Me.aLastName = aLastName
Me.aAddress = anAddress
End Sub
Private ID As Object
Public ReadOnly Property EmpID() As String
Get
Return ID.ToString()
End Get
End Property
Private aLastName As String
Public Property LastName() As String
Get
Return aLastName
End Get
Set
aLastName = value
End Set
End Property
Private aFirstName As String
Public Property FirstName() As String
Get
Return aFirstName
End Get
Set
aFirstName = value
End Set
End Property
Public ReadOnly Property FullName() As String
Get
Return FirstName & " " & LastName
End Get
End Property
Private aAddress As String
Public Property Address() As String
Get
Return aAddress
End Get
Set
aAddress = value
End Set
End Property
End Class
End Namespace
Comentários
O FormField identifica um par de nome/valor que é passado na Form coleção.The FormField identifies a name/value pair that is passed in the Form collection. Enquanto a FormField propriedade identifica o nome do par, o é FormParameter associado ao seu valor correspondente no tempo de execução.While the FormField property identifies the name of the pair, the FormParameter binds to its corresponding value at run time. Se o par nome/valor da cadeia de caracteres da variável de formulário esperado não for passado para a página da Web ASP.NET na coleção, o Evaluate método associará o parâmetro ao valor da DefaultValue propriedade, se estiver definido.If the expected form variable string name/value pair is not passed to the ASP.NET Web page in the collection, the Evaluate method binds the parameter to the value of the DefaultValue property, if it is set. Se o DefaultValue não estiver definido, o Evaluate método não vinculará o parâmetro a um valor.If the DefaultValue is not set, the Evaluate method fails to bind the parameter to a value.