C# 使用包含变量名称的字符串访问变量
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/11122241/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Accessing a variable using a string containing the variable's name
提问by Rick Price
I am reading the name of a string variable from the database (e.g. "_datafile"). I want to know how I can access a named variable within my program using this string.
我正在从数据库中读取字符串变量的名称（例如“_datafile”）。我想知道如何使用此字符串访问程序中的命名变量。
I have already tried using a dictionary, hash table, and a switch-case statement but I would like to have the variable resolve itself dynamically. Is this possible?
我已经尝试过使用字典、哈希表和 switch-case 语句，但我想让变量动态地自行解析。这可能吗？
回答by Olivier Jacot-Descombes
Usually you would create a class representing the values of one table record. If your table has an IDa FirstNameand a LastNamecolumn, you would create a class like this
通常您会创建一个类来表示一个表记录的值。如果你的表有一个IDaFirstName和一个LastName列，你会创建一个这样的类
public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
Then you create a list of persons
然后你创建一个人员列表
var people = new List<Person>();
Now you can add persons to the list.
现在您可以将人员添加到列表中。
var p = new Person();
p.ID = 5;
p.FirstName = "John";
p.LastName = "Doe";
people.Add(p);
You can use a DataReader in order to read from a table
您可以使用 DataReader 来读取表
string sql = "SELECT * FROM tblPerson WHERE LastName LIKE @pattern";
cmd = new SqlCommand(sql);
cmd.Connection = "server=test;uid=sa;pwd=manager;database=northwind";
cmd.Parameters.AddWithValue("@pattern", "A%"); // Names beginning with "A"
using (SqlDataReader reader = cmd.ExecuteReader()) {
// Get column indexes
int idOrdinal = reader.GetOrdinal("ID");
int firstNameOrdinal = reader.GetOrdinal("FirstName");
int lastNameOrdinal = reader.GetOrdinal("LastName");
while(reader.Read()) {
var p = new Person();
p.ID = reader.GetInt32(idOrdinal);
p.FirstName = reader.GetString(firstNameOrdinal);
p.LastName = reader.GetString(lastNameOrdinal);
people.Add(p);
}
}
回答by Kevin Aenmey
Do you mean you want to get the value of a field using the field name as a string?
您的意思是要使用字段名称作为字符串来获取字段的值吗？
public class MyClass
{
public string _datafile;
public MyClass()
{
_datafile = "Hello";
}
public void PrintField()
{
var result = this.GetType().GetField("_datafile").GetValue(this);
Console.WriteLine(result); // will print Hello
}
}
EDIT:@Rick, to respond to your comment:
编辑：@Rick，回应您的评论：
public class MyClass
{
public IEnumerable<string> _parameters = new[] { "Val1", "Val2", "Val3" };
public void PrintField()
{
var parameters = this.GetType().GetField("_parameters").GetValue(this) as IEnumerable;
// Prints:
// Val1
// Val2
// Val3
foreach(var item in parameters)
{
Console.WriteLine(item);
}
}
}
回答by andrews_nz
If you want to get the value of a field based on its string name you will have to use reflection.
如果您想根据字符串名称获取字段的值，则必须使用反射。
class MyClass
{
public int DataFile { get; set; }
public int _datafile;
}
var ob = new MyClass();
var typ = typeof(MyClass);
var f = typ.GetField("_datafile");
var prop = typ.GetProperty("DataFile");
var val = f.GetValue(ob);
var propVal = prop.GetValue(ob);
