C# |类型。GetField()方法
原文:https://www.geeksforgeeks.org/c-sharp-type-getfield-method/
类型。GetField()方法用于获取当前类型的特定字段。此方法的重载列表中有 2 种方法，如下所示:
- 获取字段(字符串)方法
- 方法
获取字段(字符串)方法
此方法用于搜索具有指定名称的公共字段。
*语法:*公共系统。反射. FieldInfo GetField(字符串名称)； 这里，需要包含数据字段名称的字符串来获取。
*返回值:*该方法返回一个表示具有指定名称的公共字段的对象，否则为空。
*异常:*如果名称为空，该方法抛出 ArgumentNullException 。
以下程序说明了类型的使用。GetField() 方法:
*例 1:*
// C# program to demonstrate the
// Type.GetField(String) Method
using System;
using System.Globalization;
using System.Reflection;
class GFG {
// Main Method
public static void Main()
{
// Declaring and initializing object of Type
Type objType = typeof(Student);
// try-catch block for handling Exception
try {
// Getting FieldInfo by
// using GetField(String) Method
FieldInfo info = objType.GetField("Name");
// Display the Result
Console.WriteLine("FieldInfo is: {0}", info);
}
// catch ArgumentNullException here
catch (ArgumentNullException e)
{
Console.Write("name is null.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
}
// Defining class Student
public class Student
{
public string Name = "Rahul";
public string Dept = "Electrical";
public int Roll = 10;
}
**Output:
FieldInfo is: System.String Name
```**
****示例 2:** 适用于*参数异常***
```cs
// C# program to demonstrate the
// Type.GetField(String) Method
using System;
using System.Globalization;
using System.Reflection;
class GFG {
// Main Method
public static void Main()
{
// Declaring and initializing object of Type
Type objType = typeof(Student);
// try-catch block for handling Exception
try {
// Getting FieldInfo by
// using GetField() Method
FieldInfo info = objType.GetField(null);
// Display the Result
Console.WriteLine("FieldInfo is: {0}", info);
}
// catch ArgumentNullException here
catch (ArgumentNullException e)
{
Console.WriteLine("Name is null.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
}
// Defining class Student
public class Student
{
public string Name = "Rahul";
public string Dept = "Electrical";
public int Roll = 10;
}
**Output:
name is null.
Exception Thrown: System.ArgumentNullException
```**
#### **方法**
**此方法用于使用指定的绑定约束搜索指定的字段。**
> ****语法:**公共抽象系统。反射。字段信息获取字段(字符串名称，系统。反射. binding flags binding attr)；**
>
> ****参数**:
>
> **名称**:包含要获取的数据字段名称的字符串。
> **bindingAttr** :它是一个由一个或多个 BindingFlags 组成的位掩码，指定如何进行搜索，或者返回 null 的 Zero。**
****返回值:**该方法返回一个对象，表示符合指定要求的字段，否则为空。**
****异常**:如果名称为空，该方法抛出**参数为空异常**。**
**以下程序说明了上述方法的使用:**
****例 1:****
```cs
// C# program to demonstrate the
// Type.GetField(String) Method
using System;
using System.Globalization;
using System.Reflection;
class GFG {
// Main Method
public static void Main()
{
// Declaring and initializing object of Type
Type objType = typeof(Student);
// try-catch block for handling Exception
try {
// You must specify either BindingFlags.Instance
// or BindingFlags.Static
// and Specify BindingFlags.Public
// to include public fields in the search
BindingFlags battr = BindingFlags.Public | BindingFlags.Instance;
// Getting FieldInfo by
// using GetField() Method
FieldInfo info = objType.GetField("Name", battr);
// Display the Result
Console.WriteLine("FieldInfo is: {0}", info);
}
// catch ArgumentNullException here
catch (ArgumentNullException e)
{
Console.Write("name is null.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
}
// Defining class Student
public class Student
{
public string Name = "Rahul";
public string Dept = "Electrical";
public int Roll = 10;
}
**Output:
FieldInfo is: System.String Name
```**
****示例 2:** 适用于*参数异常***
```cs
// C# program to demonstrate the
// Type.GetField(String) Method
using System;
using System.Globalization;
using System.Reflection;
class GFG {
// Main Method
public static void Main()
{
// Declaring and initializing object of Type
Type objType = typeof(Student);
// try-catch block for handling Exception
try {
// You must specify either BindingFlags.Instance
// or BindingFlags.Static
// and Specify BindingFlags.Public
// to include public fields in the search
BindingFlags battr = BindingFlags.Public | BindingFlags.Instance;
// Getting FieldInfo by
// using GetField() Method
FieldInfo info = objType.GetField(null, battr);
// Display the Result
Console.WriteLine("FieldInfo is: {0}", info);
}
// catch ArgumentNullException here
catch (ArgumentNullException e)
{
Console.WriteLine("name is null.");
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
}
// Defining class Student
public class Student
{
public string Name = "Rahul";
public string Dept = "Electrical";
public int Roll = 10;
}
*输出:*
name is null.
Exception Thrown: System.ArgumentNullException
*参考:*
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