C# Type.GetField()用法及代码示例

Type.GetField()方法用于获取当前Type的特定字段。此方法的重载列表中有2种方法，如下所示：

GetField(String)方法
GetField(String，BindingFlags)方法

GetField(String) Method

此方法用于搜索具有指定名称的公共字段。

用法： public System.Reflection.FieldInfo GetField (string name);

Here, it takes the string containing the name of the data field to get.

返回值：如果找到，则此方法返回一个具有指定名称的代表公共字段的对象，否则为null。

异常：如果名称为null，则此方法抛出ArgumentNullException。

以下示例程序旨在说明Type.GetField()方法的使用：

示例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; 
}

输出：

FieldInfo is: System.String Name

示例2:对于ArgumentNullException

// 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; 
}

输出：

name is null.
Exception Thrown: System.ArgumentNullException

GetField(String, BindingFlags) Method

此方法用于使用指定的绑定约束来搜索指定的字段。

用法： public abstract System.Reflection.FieldInfo GetField (string name, System.Reflection.BindingFlags bindingAttr);

参数：

name：包含要获取的数据字段名称的字符串。
bindingAttr：这是一个位掩码，由一个或多个BindingFlags组成，它们指定进行搜索的方式或为零，以返回null。

返回值：如果发现否则，此方法返回一个对象，该对象表示与指定要求匹配的字段，否则为null。

异常：如果name为null，则此方法将引发ArgumentNullException。

以下示例程序旨在说明上述方法的用法：

示例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 { 
  
            // 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; 
}

输出：

FieldInfo is: System.String Name

示例2:对于ArgumentNullException

// 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：

https://docs.microsoft.com/en-us/dotnet/api/system.type.getfield?view=netframework-4.8

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注：本文由纯净天空筛选整理自RohitPrasad3大神的英文原创作品 C# | Type.GetField() Method。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。