Question

我有一个包含任务的课程：

class Task{
  public string Description;
  public DateTime StartDate;
  public DateTime EndDate;
}

我有一个SQLite数据库，其DataTable名为“任务”：

DataTable.Rows[0]["Description"].ToString() // "Draw a cat"
DataTable.Rows[0]["BeginDate"].ToString() // "2016-08-17 9:47:22 AM"
DataTable.Rows[0]["EndDate"].ToString() // "2016-08-17 11:22:37 AM"

我可以创建从DataTable中填充的List<Task>吗？

我可以向Task添加新的List<Task>并让它更新DataTable吗？

Answer 1

我可以创建从DataTable填充的List吗？

你需要这样的代码才能做到这一点：

// Creates IEnumerable<DataRow>

var taskDataTableEnumerable = taskDataTable.AsEnumerable();

List<Task> myTaskList =
    (from item in taskDataTableEnumerable
     select new Task{
         Description = item.Field<string>("DescriptionColumnName"),
         StartDate = item.Field<DateTime>("StartDateColumnName"),
         EndDate = item.Field<DateTime>("EndDateColumnName")
    }).ToList();

我可以向List添加一个新任务并让它更新DataTable吗？

是的，您可以，并且您有以下选择：

查看此问题 - Convert generic List/Enumerable to DataTable?，它使用Nuget实用程序FastMember来实现相同的目标

或者

您只需在现有表格中创建一个新的DataRow，如下所示：
```
     DataRow taskDataRow = taskDataTable.NewRow();
```

使用如下代码从新添加的任务对象向taskDataRow添加数据：

       taskDataRow["DescriptionColumnName"] = taskObject.Description
       taskDataRow["StartDateColumnName"] = taskObject.StartDate
       taskDataRow["EndDateColumnName"] = taskObject.EndDate

这种方式新添加的Task对象也会DataRow添加到DataTable FastMember，以防type T对您的用例不起作用您需要一个不同的选项，然后可能计划使用下面的自定义代码，其中所有DataTable属性将转换为具有适当列名的public static DataTable CreateTable<TDataTable>(this IEnumerable<TDataTable> collection) { // Fetch the type of List contained in the ParamValue var tableType = typeof(TDataTable); // Create DataTable which will contain data from List<T> var dataTable = new DataTable(); // Fetch the Type fields count var columnCount = tableType.GetProperties().Count(); var columnNameMappingDictionary = new Dictionary<string, string>(); // Create DataTable Columns using table type field name and their types // Traversing through Column Collection for (var counter = 0; counter < columnCount; counter++) { var propertyInfo = tableType.GetProperties()[counter]; // Fetch DataParam attribute var dataParameterAttribute = propertyInfo.GetDataParameterAttribute(); // Datatable column name based on DataParam attribute var columnName = (dataParameterAttribute != null) ? dataParameterAttribute.Name : propertyInfo.Name; columnNameMappingDictionary.Add(propertyInfo.Name, (dataParameterAttribute != null) ? dataParameterAttribute.Name : propertyInfo.Name); // Fetch the current type of a property and check whether its nullable type before adding a column var currentType = tableType.GetProperties()[counter].PropertyType; dataTable.Columns.Add(columnName, Nullable.GetUnderlyingType(currentType) ?? currentType); } // Return parameter with null value if (collection == null) return dataTable; // Traverse through number of entries / rows in the List foreach (var item in collection) { // Create a new DataRow var dataRow = dataTable.NewRow(); foreach (var columnName in columnNameMappingDictionary.Select(propertyinfo => propertyinfo.Value)) { dataRow[columnName] = item.GetType().GetProperty(columnName).GetValue(item) ?? DBNull.Value; } // Add Row to Table dataTable.Rows.Add(dataRow); } return (dataTable); }，您可以根据需要添加字段选项，目前它是属性：

[AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
    public class DataParamAttribute : Attribute
    {
        /// <summary>
        /// Gets or sets the name.
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="DataParamAttribute"/> class.
        /// </summary>
        /// <param name="name">
        /// The name.
        /// </param>
        public DataParamAttribute(string name)
        {
            this.Name = name;
        }
    }

//数据参数属性

public static DataParamAttribute GetDataParameterAttribute(this PropertyInfo propertyInfo)
        {
            DataParamAttribute mappedAttribute = null;

            // Get list of Custom Attributes on a property
            var attributeArray = propertyInfo.GetCustomAttributes(false);

            // Column mapping of the ParameterAttribute
            var columnMapping =
                attributeArray.FirstOrDefault(attribute => attribute.GetType() == typeof(DataParamAttribute));

            if (columnMapping != null)
            {
                // Typecast to get the mapped attribute
                mappedAttribute = columnMapping as DataParamAttribute;
            }
            return mappedAttribute;
        }

//获取DataParameter属性

picker.delegate = self;

如何将DataTable数据绑定到自定义对象列表

1 个答案: