Reputation: 14262

How do you convert a DataTable into a generic list?

Currently, I'm using:

DataTable dt = CreateDataTableInSomeWay();

List<DataRow> list = new List<DataRow>(); 
foreach (DataRow dr in dt.Rows)
{
    list.Add(dr);
}

Is there a better/magic way?

Upvotes: 207

Answers (28)

bobt

Reputation: 11

To get List of values instead of ItemArray, do this:

List<string> s = dt.AsEnumerable().Select(x => x[0].ToString()).ToList();

The above assumes that you want list of string values from column 0.

Upvotes: 1

Ali Amini

Reputation: 416

try this using Newtonsoft Json:

var json = JsonConvert.SerializeObject(dataTable);
var YourConvertedDataType = JsonConvert.DeserializeObject<YourDataType>(json);

Upvotes: 1

mr R

Reputation: 1126

lPerson = dt.AsEnumerable().Select(s => new Person()
        {
            Name = s.Field<string>("Name"),
            SurName = s.Field<string>("SurName"),
            Age = s.Field<int>("Age"),
            InsertDate = s.Field<DateTime>("InsertDate")
        }).ToList();

Link to working DotNetFiddle Example

    using System;
    using System.Collections.Generic;   
    using System.Data;
    using System.Linq;
    using System.Data.DataSetExtensions;

    public static void Main()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("SurName", typeof(string));
        dt.Columns.Add("Age", typeof(int));
        dt.Columns.Add("InsertDate", typeof(DateTime));

        var row1= dt.NewRow();
        row1["Name"] = "Adam";
        row1["SurName"] = "Adam";
        row1["Age"] = 20;
        row1["InsertDate"] = new DateTime(2020, 1, 1);
        dt.Rows.Add(row1);

        var row2 = dt.NewRow();
        row2["Name"] = "John";
        row2["SurName"] = "Smith";
        row2["Age"] = 25;
        row2["InsertDate"] = new DateTime(2020, 3, 12);
        dt.Rows.Add(row2);

        var row3 = dt.NewRow();
        row3["Name"] = "Jack";
        row3["SurName"] = "Strong";
        row3["Age"] = 32;
        row3["InsertDate"] = new DateTime(2020, 5, 20);
        dt.Rows.Add(row3);

        List<Person> lPerson = new List<Person>();
        lPerson = dt.AsEnumerable().Select(s => new Person()
        {
            Name = s.Field<string>("Name"),
            SurName = s.Field<string>("SurName"),
            Age = s.Field<int>("Age"),
            InsertDate = s.Field<DateTime>("InsertDate")
        }).ToList();
        
        foreach(Person pers in lPerson)
        {
            Console.WriteLine("{0} {1} {2} {3}", pers.Name, pers.SurName, pers.Age, pers.InsertDate);
        }
    }   
    
    public class Person
    {
        public string Name { get; set; }
        public string SurName { get; set; }
        public int Age { get; set; }
        public DateTime InsertDate { get; set; }
    }
}

Upvotes: 3

Vikas Lalwani

Reputation: 1061

If anyone want's to create custom function to convert datatable to list

class Program
{
    static void Main(string[] args)
    {
        DataTable table = GetDataTable();
        var sw = new Stopwatch();

        sw.Start();
        LinqMethod(table);
        sw.Stop();
        Console.WriteLine("Elapsed time for Linq Method={0}", sw.ElapsedMilliseconds);

        sw.Reset();

        sw.Start();
        ForEachMethod(table);
        sw.Stop();
        Console.WriteLine("Elapsed time for Foreach method={0}", sw.ElapsedMilliseconds);

        Console.ReadKey();
    }

    private static DataTable GetDataTable()
    {
        var table = new DataTable();
        table.Columns.Add("ID", typeof(double));
        table.Columns.Add("CategoryName", typeof(string));
        table.Columns.Add("Active", typeof(double));

        var rand = new Random();

        for (int i = 0; i < 100000; i++)
        {
            table.Rows.Add(i, "name" + i,  rand.Next(0, 2));
        }
        return table;
    }

    private static void LinqMethod(DataTable table)
    {
        var list = table.AsEnumerable()
            .Skip(1)
            .Select(dr =>
                new Category
                {
                    Id = Convert.ToInt32(dr.Field<double>("ID")),
                    CategoryName = dr.Field<string>("CategoryName"),                      
                    IsActive =
                            dr.Field<double>("Active") == 1 ? true : false
                }).ToList();
    }
    private static void ForEachMethod(DataTable table)
    {
        var categoryList = new List<Category>(table.Rows.Count);
        foreach (DataRow row in table.Rows)
        {
            var values = row.ItemArray;
            var category = new Category()
            {
                Id = Convert.ToInt32(values[0]),
                CategoryName = Convert.ToString(values[1]),                   
                IsActive = (double)values[2] == 1 ? true : false
            };
            categoryList.Add(category);
        }
    }

    private class Category
    {
        public int Id { get; set; }
        public string CategoryName { get; set; }
        public bool IsActive { get; set; }
    }
}

If we execute above code, Foreach method finishes in 56ms while linq one takes 101ms ( for 1000 records). So Foreach method is better to use. Source:Ways to Convert Datatable to List in C# (with performance test example)

Upvotes: 1

hosam hemaily

Reputation: 458

you can use following two Generic functions

private static List<T> ConvertDataTable<T>(DataTable dt)
    {
        List<T> data = new List<T>();
        foreach (DataRow row in dt.Rows)
        {
            T item = GetItem<T>(row);
            data.Add(item);
        }
        return data;
    }
    private static T GetItem<T>(DataRow dr)
    {

        Type temp = typeof(T);
        T obj = Activator.CreateInstance<T>();

        foreach (DataColumn column in dr.Table.Columns)
        {
            foreach (PropertyInfo pro in temp.GetProperties())
            {
                if (pro.Name == column.ColumnName)
                    pro.SetValue(obj, dr[column.ColumnName].ToString(), null);
                else
                    continue;
            }
        }
        return obj;
    }

and use it as following

List<StudentScanExamsDTO> studentDetails = ConvertDataTable<StudentScanExamsDTO>(dt);

Upvotes: 0

Maghalakshmi Saravana

Reputation: 811

The Easiest way of Converting the DataTable into the Generic list of class

using Newtonsoft.Json;

var json = JsonConvert.SerializeObject(dataTable);
var model = JsonConvert.DeserializeObject<List<ClassName>>(json);

Upvotes: 6

Maghalakshmi Saravana

Reputation: 811

To assign the DataTable rows to the generic List of class

  List<Candidate> temp = new List<Candidate>();//List that holds the Candidate Class,
    //Note:The Candidate class contains RollNo,Name and Department
    //tb is DataTable
    temp = (from DataRow dr in tb.Rows
                        select new Candidate()
                        {
                            RollNO = Convert.ToInt32(dr["RollNO"]),
                            Name = dr["Name"].ToString(),
                            Department = dr["Department"].ToString(),

                        }).ToList();

Upvotes: -1

mohamed mostafa

Reputation: 11

Use Extension :

public static class Extensions
{
    #region Convert Datatable To List
    public static IList<T> ToList<T>(this DataTable table) where T : new()
    {
        IList<PropertyInfo> properties = typeof(T).GetProperties().ToList();
        IList<T> result = new List<T>();

        foreach (var row in table.Rows)
        {
            var item = CreateItemFromRow<T>((DataRow)row, properties);
            result.Add(item);
        }
        return result;
    }
    private static T CreateItemFromRow<T>(DataRow row, IList<PropertyInfo> properties) where T : new()
    {
        T item = new T();
        foreach (var property in properties)
        {
            property.SetValue(item, row[property.Name], null);
        }
        return item;
    }
    #endregion
}

Upvotes: 0

Anil

Reputation: 1

Converting DataTable to Generic Dictionary

public static Dictionary<object,IList<dynamic>> DataTable2Dictionary(DataTable dt)
{
    Dictionary<object, IList<dynamic>> dict = new Dictionary<dynamic, IList<dynamic>>();

    foreach(DataColumn column in dt.Columns)
    {
        IList<dynamic> ts = dt.AsEnumerable()
                              .Select(r => r.Field<dynamic>(column.ToString()))
                              .ToList();
        dict.Add(column, ts);
    }
    return dict;
}

Upvotes: 0

Ömer Ceylan

Reputation: 25

You can use a generic method like that for datatable to generic list

public static List<T> DataTableToList<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);
                    if (propertyInfo.PropertyType.IsEnum)
                    {
                        propertyInfo.SetValue(obj, Enum.Parse(propertyInfo.PropertyType, row[prop.Name].ToString()));
                    }
                    else
                    {
                        propertyInfo.SetValue(obj, Convert.ChangeType(row[prop.Name], propertyInfo.PropertyType), null);
                    }                          
                }
                catch
                {
                    continue;
                }
            }

            list.Add(obj);
        }

        return list;
    }
    catch
    {
        return null;
    }
}

Upvotes: 0

Bondaryuk Vladimir

Reputation: 519

I have added some modification to the code from this answer (https://stackoverflow.com/a/24588210/4489664) because for nullable Types it will return exception

public static List<T> DataTableToList<T>(this DataTable table) where T: new()
{
    List<T> list = new List<T>();
    var typeProperties = typeof(T).GetProperties().Select(propertyInfo => new
        {
            PropertyInfo = propertyInfo,
            Type = Nullable.GetUnderlyingType(propertyInfo.PropertyType) ?? propertyInfo.PropertyType
        }).ToList();

    foreach (var row in table.Rows.Cast<DataRow>())
    {
        T obj = new T();
        foreach (var typeProperty in typeProperties)
        {
            object value = row[typeProperty.PropertyInfo.Name];
            object safeValue = value == null || DBNull.Value.Equals(value)
                ? null
                : Convert.ChangeType(value, typeProperty.Type);

            typeProperty.PropertyInfo.SetValue(obj, safeValue, null);
        }
        list.Add(obj);
    }
    return list;
}

Upvotes: 16

Saurin

Reputation: 1830

        /* This is a generic method that will convert any type of DataTable to a List 
         * 
         * 
         * Example :    List< Student > studentDetails = new List< Student >();  
         *              studentDetails = ConvertDataTable< Student >(dt);  
         *
         * Warning : In this case the DataTable column's name and class property name
         *           should be the same otherwise this function will not work properly
         */

The following are the two functions in which if we pass a DataTable and a user defined class. It will then return the List of that class with the DataTable data.

        public static List<T> ConvertDataTable<T>(DataTable dt)
        {
            List<T> data = new List<T>();
            foreach (DataRow row in dt.Rows)
            {
                T item = GetItem<T>(row);
                data.Add(item);
            }
            return data;
        }


        private static T GetItem<T>(DataRow dr)
        {
            Type temp = typeof(T);
            T obj = Activator.CreateInstance<T>();

            foreach (DataColumn column in dr.Table.Columns)
            {
                foreach (PropertyInfo pro in temp.GetProperties())
                {
                   //in case you have a enum/GUID datatype in your model
                   //We will check field's dataType, and convert the value in it.
                    if (pro.Name == column.ColumnName){                
                    try
                    {
                        var convertedValue = GetValueByDataType(pro.PropertyType, dr[column.ColumnName]);
                        pro.SetValue(obj, convertedValue, null);
                    }
                    catch (Exception e)
                    {         
                       //ex handle code                   
                        throw;
                    }
                        //pro.SetValue(obj, dr[column.ColumnName], null);
                }
                    else
                        continue;
                }
            }
            return obj;
        }

This method will check the datatype of field, and convert dataTable value in to that datatype.

    private static object GetValueByDataType(Type propertyType, object o)
    {
        if (o.ToString() == "null")
        {
            return null;
        }
        if (propertyType == (typeof(Guid)) || propertyType == typeof(Guid?))
        {
            return Guid.Parse(o.ToString());
        }
        else if (propertyType == typeof(int) || propertyType.IsEnum) 
        {
            return Convert.ToInt32(o);
        }
        else if (propertyType == typeof(decimal) )
        {
            return Convert.ToDecimal(o);
        }
        else if (propertyType == typeof(long))
        {
            return Convert.ToInt64(o);
        }
        else if (propertyType == typeof(bool) || propertyType == typeof(bool?))
        {
            return Convert.ToBoolean(o);
        }
        else if (propertyType == typeof(DateTime) || propertyType == typeof(DateTime?))
        {
            return Convert.ToDateTime(o);
        }
        return o.ToString();
    }

To call the preceding method, use the following syntax:

List< Student > studentDetails = new List< Student >();  
studentDetails = ConvertDataTable< Student >(dt);

Change the Student class name and dt value based on your requirements. In this case the DataTable column's name and class property name should be the same otherwise this function will not work properly.

Upvotes: 2

syed ali abbas

Reputation: 49

DataTable dt;   // datatable should contains datacolumns with Id,Name

List<Employee> employeeList=new List<Employee>();  // Employee should contain  EmployeeId, EmployeeName as properties

foreach (DataRow dr in dt.Rows)
{
    employeeList.Add(new Employee{EmployeeId=dr.Id,EmplooyeeName=dr.Name});
}

Upvotes: 4

Nathan

Reputation: 153

// this is better suited for expensive object creation/initialization
IEnumerable<Employee> ParseEmployeeTable(DataTable dtEmployees)
{
    var employees = new ConcurrentBag<Employee>();

    Parallel.ForEach(dtEmployees.AsEnumerable(), (dr) =>
    {
        employees.Add(new Employee() 
        {
            _FirstName = dr["FirstName"].ToString(),
            _LastName = dr["Last_Name"].ToString()
        });
    });

    return employees;
}

Upvotes: 6

Jayaprakash

Reputation: 69

We can use a Generic Method for converting DataTable to List instead of manually converting a DataTable to List.

Note: DataTable's ColumnName and Type's PropertyName should be same.

Call the below Method:

long result = Utilities.ConvertTo<Student>(dt ,out listStudent);

// Generic Method
public class Utilities
{
    public static long ConvertTo<T>(DataTable table, out List<T> entity)
    {
        long returnCode = -1;
        entity = null;

        if (table == null)
        {
            return -1;
        }

        try
        {
            entity = ConvertTo<T>(table.Rows);
            returnCode = 0;
        }

        catch (Exception ex)
        {
            returnCode = 1000;
        }

        return returnCode;
    }

    static List<T> ConvertTo<T>(DataRowCollection rows)
    {
        List<T> list = null;
        if (rows != null)
        {
            list = new List<T>();

            foreach (DataRow row in rows)
            {
                T item = CreateItem<T>(row);
                list.Add(item);
            }
        }

        return list;
    }

    static T CreateItem<T>(DataRow row)
    {
        string str = string.Empty;
        string strObj = string.Empty;

        T obj = default(T);

        if (row != null)
        {
            obj = Activator.CreateInstance<T>();
            strObj = obj.ToString();
            NameValueCollection objDictionary = new NameValueCollection();

            foreach (DataColumn column in row.Table.Columns)
            {
                PropertyInfo prop = obj.GetType().GetProperty(column.ColumnName);

                if (prop != null)
                {
                    str = column.ColumnName;

                    try
                    {
                        objDictionary.Add(str, row[str].ToString());
                        object value = row[column.ColumnName];
                        Type vType = obj.GetType();

                        if (value == DBNull.Value)
                        {
                            if (vType == typeof(int) || vType == typeof(Int16)
                                                     || vType == typeof(Int32)
                                                     || vType == typeof(Int64)
                                                     || vType == typeof(decimal)
                                                     || vType == typeof(float)
                                                     || vType == typeof(double))
                            {
                                value = 0;
                            }

                            else if (vType == typeof(bool))
                            {
                                value = false;
                            }

                            else if (vType == typeof(DateTime))
                            {
                                value = DateTime.MaxValue;
                            }

                            else
                            {
                                value = null;
                            }

                            prop.SetValue(obj, value, null);
                        }

                        else
                        {
                            prop.SetValue(obj, value, null);
                        }
                    }

                    catch(Exception ex)
                    {

                    }
                }
            }

            PropertyInfo ActionProp = obj.GetType().GetProperty("ActionTemplateValue");

            if (ActionProp != null)
            {
                object ActionValue = objDictionary;
                ActionProp.SetValue(obj, ActionValue, null);
            }
        }

        return obj;
    }
}

Upvotes: 1

mrtwin

Reputation: 1

Output

public class ModelUser
{
    #region Model

    private string _username;
    private string _userpassword;
    private string _useremail;
    private int _userid;

    /// <summary>
    /// 
    /// </summary>
    public int userid
    {
        set { _userid = value; }
        get { return _userid; }
    }


    /// <summary>
    /// 
    /// </summary>

    public string username
    {
        set { _username = value; }
        get { return _username; }
    }

    /// <summary>
    /// 
    /// </summary>
    public string useremail
    {
        set { _useremail = value; }
        get { return _useremail; }
    }

    /// <summary>
    /// 
    /// </summary>
    public string userpassword
    {
        set { _userpassword = value; }
        get { return _userpassword; }
    }
    #endregion Model
}

public List<ModelUser> DataTableToList(DataTable dt)
{
    List<ModelUser> modelList = new List<ModelUser>();
    int rowsCount = dt.Rows.Count;
    if (rowsCount > 0)
    {
        ModelUser model;
        for (int n = 0; n < rowsCount; n++)
        {
            model = new ModelUser();

            model.userid = (int)dt.Rows[n]["userid"];
            model.username = dt.Rows[n]["username"].ToString();
            model.useremail = dt.Rows[n]["useremail"].ToString();
            model.userpassword = dt.Rows[n]["userpassword"].ToString();

            modelList.Add(model);
        }
    }
    return modelList;
}

static DataTable GetTable()
{
    // Here we create a DataTable with four columns.
    DataTable table = new DataTable();
    table.Columns.Add("userid", typeof(int));
    table.Columns.Add("username", typeof(string));
    table.Columns.Add("useremail", typeof(string));
    table.Columns.Add("userpassword", typeof(string));

    // Here we add five DataRows.
    table.Rows.Add(25, "Jame", "[email protected]", DateTime.Now.ToString());
    table.Rows.Add(50, "luci", "[email protected]", DateTime.Now.ToString());
    table.Rows.Add(10, "Andrey", "[email protected]", DateTime.Now.ToString());
    table.Rows.Add(21, "Michael", "[email protected]", DateTime.Now.ToString());
    table.Rows.Add(100, "Steven", "[email protected]", DateTime.Now.ToString());
    return table;
}

protected void Page_Load(object sender, EventArgs e)
{
    List<ModelUser> userList = new List<ModelUser>();

    DataTable dt = GetTable();

    userList = DataTableToList(dt);

    gv.DataSource = userList;
    gv.DataBind();
}[enter image description here][1]

</asp:GridView>
</div>

Upvotes: 0

Jon Skeet

Reputation: 1503300

If you're using .NET 3.5, you can use DataTableExtensions.AsEnumerable (an extension method) and then if you really need a List<DataRow> instead of just IEnumerable<DataRow> you can call Enumerable.ToList:

IEnumerable<DataRow> sequence = dt.AsEnumerable();

using System.Linq;
...
List<DataRow> list = dt.AsEnumerable().ToList();

Upvotes: 304

shigeno

Reputation:

A more 'magic' way, and doesn't need .NET 3.5.

If, for example, DBDatatable was returning a single column of Guids (uniqueidentifier in SQL) then you could use:

Dim gList As New List(Of Guid)
gList.AddRange(DirectCast(DBDataTable.Select(), IEnumerable(Of Guid)))

Upvotes: 5

Rahul Garg

Reputation: 4349

You can create a extension function as :

public static List<T> ToListof<T>(this DataTable dt)
{
    const BindingFlags flags = BindingFlags.Public | BindingFlags.Instance;
    var columnNames = dt.Columns.Cast<DataColumn>()
        .Select(c => c.ColumnName)
        .ToList();
    var objectProperties = typeof(T).GetProperties(flags);
    var targetList = dt.AsEnumerable().Select(dataRow =>
    {
        var instanceOfT = Activator.CreateInstance<T>();

        foreach (var properties in objectProperties.Where(properties => columnNames.Contains(properties.Name) && dataRow[properties.Name] != DBNull.Value))
        {
            properties.SetValue(instanceOfT, dataRow[properties.Name], null);
        }
        return instanceOfT;
    }).ToList();

    return targetList;
}


var output = yourDataInstance.ToListof<targetModelType>();

Upvotes: 19

rajashekar

Reputation: 21

Use System.Data namespace then you will get .AsEnumerable().

Upvotes: 1

Levi

Reputation: 21

This worked for me: Need at least .Net Framework 3.5, Code below displays DataRow turned to Generic.IEnumerable, comboBox1 has been used for a better illustration.

using System.Linq;

DataTable dt = new DataTable();            
dt = myClass.myMethod();                 
List<object> list = (from row in dt.AsEnumerable() select (row["name"])).ToList();
comboBox1.DataSource = list;

Upvotes: 0

Kibbee

Reputation: 66152

You could use

List<DataRow> list = new List<DataRow>(dt.Select());

dt.Select() will return all rows in your table, as an array of datarows, and the List constructor accepts that array of objects as an argument to initially fill your list with.

Upvotes: 38

Stuart

Reputation: 669

If you just want a list of values from the "ID" int field returned, you could use...

List<int> ids = (from row in dt.AsEnumerable() select Convert.ToInt32(row["ID"])).ToList();

Upvotes: 17

Morteza

Reputation: 2428

using System.Data;


var myEnumerable = myDataTable.AsEnumerable();

List<MyClass> myClassList =
    (from item in myEnumerable
     select new MyClass{
         MyClassProperty1 = item.Field<string>("DataTableColumnName1"),
         MyClassProperty2 = item.Field<string>("DataTableColumnName2")
    }).ToList();

Upvotes: 11

darshan pandya

Reputation: 711

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

//Maintaining DataTable on ViewState
//For Demo only

DataTable dt = ViewState["CurrentEmp"] as DataTable;

//read data from DataTable 
//using lamdaexpression


emp = (from DataRow row in dt.Rows

   select new Employee
   {
       _FirstName = row["FirstName"].ToString(),
       _LastName = row["Last_Name"].ToString()

   }).ToList();

Upvotes: 71

user_v

Reputation: 10114

DataTable.Select() doesnt give the Rows in the order they were present in the datatable.

If order is important I feel iterating over the datarow collection and forming a List is the right way to go or you could also use overload of DataTable.Select(string filterexpression, string sort).

But this overload may not handle all the ordering (like order by case ...) that SQL provides.

Upvotes: 3

Guilherme Duarte

Reputation: 3441

Again, using 3.5 you may do it like:

dt.Select().ToList()

BRGDS

Upvotes: 7

Marc Gravell

Reputation: 1064054

With C# 3.0 and System.Data.DataSetExtensions.dll,

List<DataRow> rows = table.Rows.Cast<DataRow>().ToList();

Upvotes: 44

How do you convert a DataTable into a generic list?

Answers (28)

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