Convert DataTable to List

Question

I have an strongly typed DataTable of type MyType, I\'d like convert it in a List.

How can I do this ?

Thanks.

Answer 1

1. IEnumerable<DataRow> rows = dataTable.AsEnumerable(); (System.Data.DataSetExtensions.dll)
2. IEnumerable<DataRow> rows = dataTable.Rows.OfType<DataRow>(); (System.Core.dll)

Answer 2

The method ConvertToList that is posted below and uses reflection works perfectly for me. Thanks.

I made a slight modification to make it work with conversions on the T property types.

public List<T> ConvertToList<T>(DataTable dt)
{
    var columnNames = dt.Columns.Cast<DataColumn>()
            .Select(c => c.ColumnName)
            .ToList();
    var properties = typeof(T).GetProperties();
    return dt.AsEnumerable().Select(row =>
    {
        var objT = Activator.CreateInstance<T>();
        foreach (var pro in properties)
        {
            if (columnNames.Contains(pro.Name))
            {
                 PropertyInfo pI = objT.GetType().GetProperty(pro.Name);
                 pro.SetValue(objT, row[pro.Name] == DBNull.Value ? null : Convert.ChangeType(row[pro.Name], pI.PropertyType));
            }
        }
        return objT;
   }).ToList();
}

Hope it helps. Regards.

Answer 3

you can convert your datatable to list. check the following link

https://stackoverflow.com/a/35171050/1805776

public static class Helper
{
    public static List<T> DataTableToList<T>(this DataTable dataTable) where T : new()
    {
        var dataList = new List<T>();

        //Define what attributes to be read from the class
        const System.Reflection.BindingFlags flags = System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance;

        //Read Attribute Names and Types
        var objFieldNames = typeof(T).GetProperties(flags).Cast<System.Reflection.PropertyInfo>().
            Select(item => new
            {
                Name = item.Name,
                Type = Nullable.GetUnderlyingType(item.PropertyType) ?? item.PropertyType
            }).ToList();

        //Read Datatable column names and types
        var dtlFieldNames = dataTable.Columns.Cast<DataColumn>().
            Select(item => new
            {
                Name = item.ColumnName,
                Type = item.DataType
            }).ToList();

        foreach (DataRow dataRow in dataTable.AsEnumerable().ToList())
        {
            var classObj = new T();

            foreach (var dtField in dtlFieldNames)
            {
                System.Reflection.PropertyInfo propertyInfos = classObj.GetType().GetProperty(dtField.Name);

                var field = objFieldNames.Find(x => x.Name == dtField.Name);

                if (field != null)
                {

                    if (propertyInfos.PropertyType == typeof(DateTime))
                    {
                        propertyInfos.SetValue
                        (classObj, convertToDateTime(dataRow[dtField.Name]), null);
                    }
                    else if (propertyInfos.PropertyType == typeof(Nullable<DateTime>))
                    {
                        propertyInfos.SetValue
                        (classObj, convertToDateTime(dataRow[dtField.Name]), null);
                    }
                    else if (propertyInfos.PropertyType == typeof(int))
                    {
                        propertyInfos.SetValue
                        (classObj, ConvertToInt(dataRow[dtField.Name]), null);
                    }
                    else if (propertyInfos.PropertyType == typeof(long))
                    {
                        propertyInfos.SetValue
                        (classObj, ConvertToLong(dataRow[dtField.Name]), null);
                    }
                    else if (propertyInfos.PropertyType == typeof(decimal))
                    {
                        propertyInfos.SetValue
                        (classObj, ConvertToDecimal(dataRow[dtField.Name]), null);
                    }
                    else if (propertyInfos.PropertyType == typeof(String))
                    {
                        if (dataRow[dtField.Name].GetType() == typeof(DateTime))
                        {
                            propertyInfos.SetValue
                            (classObj, ConvertToDateString(dataRow[dtField.Name]), null);
                        }
                        else
                        {
                            propertyInfos.SetValue
                            (classObj, ConvertToString(dataRow[dtField.Name]), null);
                        }
                    }
                    else
                    {

                        propertyInfos.SetValue
                            (classObj, Convert.ChangeType(dataRow[dtField.Name], propertyInfos.PropertyType), null);

                    }
                }
            }
            dataList.Add(classObj);
        }
        return dataList;
    }

    private static string ConvertToDateString(object date)
    {
        if (date == null)
            return string.Empty;

        return date == null ? string.Empty : Convert.ToDateTime(date).ConvertDate();
    }

    private static string ConvertToString(object value)
    {
        return Convert.ToString(ReturnEmptyIfNull(value));
    }

    private static int ConvertToInt(object value)
    {
        return Convert.ToInt32(ReturnZeroIfNull(value));
    }

    private static long ConvertToLong(object value)
    {
        return Convert.ToInt64(ReturnZeroIfNull(value));
    }

    private static decimal ConvertToDecimal(object value)
    {
        return Convert.ToDecimal(ReturnZeroIfNull(value));
    }

    private static DateTime convertToDateTime(object date)
    {
        return Convert.ToDateTime(ReturnDateTimeMinIfNull(date));
    }

    public static string ConvertDate(this DateTime datetTime, bool excludeHoursAndMinutes = false)
    {
        if (datetTime != DateTime.MinValue)
        {
            if (excludeHoursAndMinutes)
                return datetTime.ToString("yyyy-MM-dd");
            return datetTime.ToString("yyyy-MM-dd HH:mm:ss.fff");
        }
        return null;
    }
    public static object ReturnEmptyIfNull(this object value)
    {
        if (value == DBNull.Value)
            return string.Empty;
        if (value == null)
            return string.Empty;
        return value;
    }
    public static object ReturnZeroIfNull(this object value)
    {
        if (value == DBNull.Value)
            return 0;
        if (value == null)
            return 0;
        return value;
    }
    public static object ReturnDateTimeMinIfNull(this object value)
    {
        if (value == DBNull.Value)
            return DateTime.MinValue;
        if (value == null)
            return DateTime.MinValue;
        return value;
    }
}

Answer 4

Assuming your DataRows inherit from your own type, say MyDataRowType, this should work:

List<MyDataRowType> list = new List<MyDataRowType>();

foreach(DataRow row in dataTable.Rows)
{
    list.Add((MyDataRowType)row);
}

This is assuming, as you said in a comment, that you're using .NET 2.0 and don't have access to the LINQ extension methods.

Answer 5

There are Linq extension methods for DataTable.

Add reference to: System.Data.DataSetExtensions.dll

Then include the namespace: using System.Data.DataSetExtensions

Finally you can use Linq extensions on DataSet and DataTables:

var matches = myDataSet.Tables.First().Where(dr=>dr.Field<int>("id") == 1);

On .Net 2.0 you can still add generic method:

public static List<T> ConvertRowsToList<T>( DataTable input, Convert<DataRow, T> conversion) {
    List<T> retval = new List<T>()
    foreach(DataRow dr in input.Rows)
        retval.Add( conversion(dr) );

    return retval;
}

Answer 6

The following does it in a single line:

dataTable.Rows.OfType<DataRow>()
    .Select(dr => dr.Field<MyType>(columnName)).ToList();

[Edit: Add a reference to System.Data.DataSetExtensions to your project if this does not compile]