如何在 C# 中将 DataTable 转换为通用列表 [重复]

Question

我需要将 C# DataTable 转换为通用集合列表

DataTable Columns Respectively

 1. EmpId  (this is Int DataType)
 2. EmpName   (this is varchar DataType)
 3. EmpAddress  (this is varchar DataType)
 4. EmpPhone  (this is varchar DataType)
 5. Status   (this is Boolean DataType)
 6. EmpRelationKey (this is int DataType)

所以我的 DataTable 包含上述字段的值。在这里我需要将此值分配到我的列表中

我的列表变量分别

class Employee
{
protected int EmpId  ;
protected string EmpName =String.Empty;
protected string EmpAddress  = String.Empty;
protected string EmpPhone  = String.Empty;
protected bool Status ;
protected int EmpRelationKey ;
}

Declaring List
List<Employee> Emp= new List<Employee>

所以现在我需要将 DataTable 值分配给这个列表。代码应该很专业。

这个方法我试过了

List<Employee>employees = new List<Employee>();  

foreach (DataRow row in dt.Rows)  
{  
   employees.Add(new Employee  
   {  
   EmpId  = Convert.ToInt32(row["EmpId"]), 
   EmpName = row["EmpName"].ToString() ,
   EmpAddress =   row["EmpName"].ToString(),
   Emphone =   row["EmpPhone"].ToString(),
   Status = Convert.toBoolean(row["Status"])
   });  
}   

但我不想提及列名，有没有其他方法可以在不提及 DataTable 中的每个列名的情况下分配值

Answer 1

using System.Reflection;

那么，

public static List<T> BindList<T>(DataTable dt)
{
    // Example 1:
    // Get private fields + non properties
    //var fields = typeof(T).GetFields(BindingFlags.NonPublic | BindingFlags.Instance);

    // Example 2: Your case
    // Get all public fields
    var fields = typeof(T).GetFields();

    List<T> lst = new List<T>();

    foreach (DataRow dr in dt.Rows)
    {
        // Create the object of T
        var ob = Activator.CreateInstance<T>();

        foreach (var fieldInfo in fields)
        {
            foreach (DataColumn dc in dt.Columns)
            {
                // Matching the columns with fields
                if (fieldInfo.Name == dc.ColumnName)
                {
                    // Get the value from the datatable cell
                    object value = dr[dc.ColumnName];

                    // Set the value into the object
                    fieldInfo.SetValue(ob, value);
                    break;
                }
            }
        }

        lst.Add(ob);
    }

    return lst;
}

使用示例：

DataTable dt1 = SqlHelper.GetTable("select * from employee;");
List<Employee> employees = BindList<Employee>(dt1);

DataTable dt2 = SqlHelper.GetTable("select * from membership;");
List<Membership> lstMembership = BindList<Membership>(dt2);

DataTable dt3 = SqlHelper.GetTable("select * from car order by name;");
List<Car> lstCar = BindList<Car>(dt3);

======================

加长版

以上示例假设 DataTable 中保存的数据与 Class 对象 的字段具有相同的数据类型。

如果数据与您的类对象的字段不同怎么办？

如null？

因此，您可能需要扩展该方法以防万一两种数据类型不相同。

public static List<T> BindList<T>(DataTable dt)
{
    // Example 1:
    // Get private fields + non properties
    //var fields = typeof(T).GetFields(BindingFlags.NonPublic | BindingFlags.Instance);

    // Example 2: Your case
    // Get all public fields
    var fields = typeof(T).GetFields();

    List<T> lst = new List<T>();

    foreach (DataRow dr in dt.Rows)
    {
        // Create the object of T
        var ob = Activator.CreateInstance<T>();

        foreach (var fieldInfo in fields)
        {
            foreach (DataColumn dc in dt.Columns)
            {
                // Matching the columns with fields
                if (fieldInfo.Name == dc.ColumnName)
                {
                    Type type = fieldInfo.FieldType;

                    // Get the value from the datatable cell
                    object value = GetValue(dr[dc.ColumnName], type);

                    // Set the value into the object
                    fieldInfo.SetValue(ob, value);
                    break;
                }
            }
        }

        lst.Add(ob);
    }

    return lst;
}

static object GetValue(object ob, Type targetType)
{
    if (targetType == null)
    {
        return null;
    }
    else if (targetType == typeof(String))
    {
        return ob + "";
    }
    else if (targetType == typeof(int))
    {
        int i = 0;
        int.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(short))
    {
        short i = 0;
        short.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(long))
    {
        long i = 0;
        long.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(ushort))
    {
        ushort i = 0;
        ushort.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(uint))
    {
        uint i = 0;
        uint.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(ulong))
    {
        ulong i = 0;
        ulong.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(double))
    {
        double i = 0;
        double.TryParse(ob + "", out i);
        return i;
    }
    else if (targetType == typeof(DateTime))
    {
        // do the parsing here...
    }
    else if (targetType == typeof(bool))
    {
        // do the parsing here...
    }
    else if (targetType == typeof(decimal))
    {
        // do the parsing here...
    }
    else if (targetType == typeof(float))
    {
        // do the parsing here...
    }
    else if (targetType == typeof(byte))
    {
        // do the parsing here...
    }
    else if (targetType == typeof(sbyte))
    {
        // do the parsing here...
    }
    else if........
    ..................

    return ob;
}

Answer 2

你可以试试这样的：

List<Employee> listObject = dTable.AsEnumerable()
                                  .Select(x => new Employee()
                                  {
                                    EmpId = x.Field<int>("EmpId"),
                                    EmpName = x.Field<string>("EmpName"),
                                    EmpAddress = x.Field<string>("EmpName"),
                                    EmpPhone = x.Field<string>("EmpPhone"),
                                    Status = x.Field<bool>("Status"),
                                    EmpRelationKey = x.Field<int>("EmpRelationKey")
                                  }).ToList();

Answer 3

使用 LinQ 你可以做到，

  List<DataRow> list = Datatablle.AsEnumerable().ToList();

更新答案。创建 Helper 类以将 Datatable 转换为 List

public static class Helper
{

    public static List<T> ConvertDataTableToList<T>(this DataTable table) where T : class, new()
    {
        try
        {
            List<T> list = new List<T>();

            foreach (var row in table.AsEnumerable())
            {
                T obj = new T();

                foreach (var prop in obj.GetType().GetProperties())
                {
                    try
                    {
                        PropertyInfo propertyInfo = obj.GetType().GetProperty(prop.Name);
                        propertyInfo.SetValue(obj, Convert.ChangeType(row[prop.Name], propertyInfo.PropertyType), null);
                    }
                    catch
                    {
                        continue;
                    }
                }

                list.Add(obj);
            }

            return list;
        }
        catch
        {
            return null;
        }
    }
}

那么，

DataTable dtDatatable = GetEmployee();
List<Employee> employeeList = dtDatatable.ConvertDataTableToList<Employee>();

Answer 4

正如评论中提到的，每当您在DataTable 结构中进行任何更改时，这些更改也必须在Class 中完成，如果您更改Class，则将这些更改与DataTable 结构同步。

List<Employee>employees = new List<Employee>();  

foreach (DataRow row in dt.Rows)  
{  
    Employee emp= new Employee();

    PropertyInfo[] properties = typeof(Employee).GetProperties();
    for (int i = 0; i < properties.Length; i++)
    {
        property.SetValue(emp, Convert.ChangeType(row[i], property.GetType()));
    }
}

别忘了using System.Reflection;