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Linq使用包含字段名称的字符串选择单个字段

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假设我有一个简单的对象列表，如下所示：

public class DataField
{
    public int DataFieldId {get; set;}
    public int KeyId {get; set;}
    public string FieldName {get; set;}
    public string Data {get; set;}
}

现在我想使用Property名称的字符串值获取Property中的值列表，如下所示：

public List<string> getFieldData(List<DataField> dataToSearch, string propertyName)
{
    // This is the area I'd like to figure out.
    return dataToSearch.Select(ds => ds.propertyName).Distinct.ToList();
}

public void MyMethod()
{
    var data = new List<DataField>{
        new DataField{DataFieldId = 1, KeyId = 1,
            FieldName = "UserName", Data = "jSmith"},
        new DataField{DataFieldId = 2, KeyId = 1,
            FieldName = "Email", Data = "jSmith@nowhere.com"},
        new DataField{DataFieldId = 3, KeyId = 1,
            FieldName = "PreferredContact", Data = "Phone"},
        new DataField{DataFieldId = 4, KeyId = 2,
            FieldName = "UserName", Data = "jDoe"},
        new DataField{DataFieldId = 5,KeyId = 2,
            FieldName = "Email", Data = "janeDoe@emailServer.net"},
        new DataField{DataFieldId = 6, KeyId = 2,
            FieldName = "PreferredContact", Data = "Email"}
    };

    // Notice I want to search using a string
    var fieldNames = getFieldData(data, "FieldName");
}

我希望fieldNames是 List<string> 包含：
"UserName"
"Email"
"PreferredContact"

我想使用一个字符串来指定要返回的列 .

c# linq

1 回答

  • 4

    你可以使用反射 . 你're using 2441852 but the class actually contains properties, so use reflection' s GetProperty() 方法 . 如果您改用字段，请使用 GetField()

    public static List<string> getFieldData(List<DataField> dataToSearch, string fieldName)
{
    // You can use reflection to get information from types at runtime.
    // The property_info variable will hold various data about the field
    // name you pass in (type, name, etc)
    var property_info = typeof(DataField).GetProperty(fieldName);

    // We can then call property_info's GetValue() on an instantiated 
    // object of our class, and it will return the value of that property on that object
    return dataToSearch.Select(ds => Convert.ToString(property_info.GetValue(ds))).Distinct().ToList();
}

    PropertyInfo类：https://msdn.microsoft.com/en-us/library/system.reflection.propertyinfo(v=vs.110).aspx

    输入类：https://msdn.microsoft.com/en-us/library/system.type(v=vs.110).aspx

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