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Can't add new row to a datatable [c#]

I have a dataset, which is stored in XML file. When application starts and XML file doesn't exists yet, I want to add some rows to my dataset and save it in XML. I use following code to do it:
partiesDb = new Parties();
//...
DataTable partyDsTable = partiesDb.Tables["party"]; //partiesDb is DataSet object
for (int i = 0; i < size; i++)
{
DataRow row = partyDsTable.NewRow(); // HERE THE CODE STOPS
row["sth"] = sth;
row["sth"] = "0";
row["id"] = "1";
if (!partyDsTable.Rows.Contains(row))
{
partyDsTable.Rows.Add(row);
}
}
System.Windows.Forms.MessageBox.Show(partyDsTable.Rows[0]["sth"].ToString());
partiesDb.WriteXml(path);
and nothing happens. Even messagebox doesn't show. The function just stop when creating a new row, and I don't know why. Can you help me?
[EDIT]:
This code works fine:
partiesDb = new Parties();
DataTable dsTable = partiesDb.Tables["party"];
DataRow dsRow = dsTable.NewRow();
dsRow["name"] = "";
dsRow["id"] = "";
dsRow["votes"] = "";
dsTable.Rows.Add(dsRow);
partiesDb.WriteXml(partiesDbPath);
I don't know why this works, but when I add loop it doesnt...

You can't add something to a null variable. So, you need to instantiate the partyDsTable if it is null.
DataTable partyDsTable = partiesDb.Tables["party"]; //partiesDb is DataSet object
if(partyDsTable == null) // instantiate it
partyDsTable = new DataTable();
for (int i = 0; i < size; i++)
{
....

DataTable partyDsTable = partiesDb.Tables["party"]; //partiesDb is DataSet object
for (int i = 0; i < size; i++)// "size" does not look like it's set to anything. If "size" is 0, then the loop will not loop.
{
partyDsTable.Rows.Add(new object[] {sth,"0","1"});//you should probably make the columns into the correct type if you are using integers.
}
System.Windows.Forms.MessageBox.Show(partyDsTable.Rows[0]["sth"].ToString());
partiesDb.WriteXml(path);

Also, if you create a class with fields that match the items in your database table, you can do all kinds of things with reflection to make usre your data is always good:
public static DataTable create_DataTable_From_Generic_Class(Type t)
{
DataTable d = new DataTable();
FieldInfo[] fI = t.GetFields();
for(int i = 0; i < fI.Length; i++)
{
DataColumn dC = new DataColumn(fI[i].Name, fI[i].FieldType);
d.Columns.Add(dC);
}
return d;
}
public static object[] Create_Datatable_Row_From_Generic_Class(Type t, object instance,DataTable dt)
{
FieldInfo[] f = t.GetFields();
object[] ret = new object[f.Length];
for (int i = 0; i < dt.Columns.Count; i++)
{
ret[i] = t.GetField(dt.Columns[i].ColumnName).GetValue(instance);
}
return ret;
}
public static List<string[]> getParams(Type type, bool convertToSQL)
{
List<string[]> ret = new List<string[]>();
Dictionary<string, object> properties = new Dictionary<string, object>();
foreach (FieldInfo prop in type.GetFields())
properties.Add(prop.Name, prop.FieldType);
foreach (string key in properties.Keys)
{
string[] r = { key, properties[key].ToString().Replace("System.", "") };
ret.Add(r);
}
if (convertToSQL)
{
return convertFromNetToSQLDataTypes(ret);
}
else
{
return ret;
}
}
private static List<string[]> convertFromNetToSQLDataTypes(List<string[]> list)
{
foreach (string[] data in list)
{
data[1] = data[1].Replace("Int16", "tinyint");
data[1] = data[1].Replace("Int32", "int");
data[1] = data[1].Replace("Int64", "bigint");
data[1] = data[1].Replace("Double", "float");
data[1] = data[1].Replace("Boolean", "tinyint");
data[1] = data[1].Replace("Double", "float");
data[1] = data[1].Replace("Long", "bigint");
data[1] = data[1].Replace("String", "varchar(100)");
}
return list;
}
public static object[] sql_Reader_To_Type(Type t, SqlDataReader r)
{
List<object> ret = new List<object>();
while (r.Read())
{
FieldInfo[] f = t.GetFields();
object o = Activator.CreateInstance(t);
for (int i = 0; i < f.Length; i++)
{
string thisType = f[i].FieldType.ToString();
switch (thisType)
{
case "System.String":
f[i].SetValue(o, Convert.ToString(r[f[i].Name]));
break;
case "System.Int16":
f[i].SetValue(o, Convert.ToInt16(r[f[i].Name]));
break;
case "System.Int32":
f[i].SetValue(o, Convert.ToInt32(r[f[i].Name]));
break;
case "System.Int64":
f[i].SetValue(o, Convert.ToInt64(r[f[i].Name]));
break;
case "System.Double":
// Console.WriteLine("converting " + f[i].Name + " to double");
double th;
if (r[f[i].Name] == null)
{
th = 0;
}
else
{
if (r[f[i].Name].GetType() == typeof(DBNull))
{
th = 0;
}
else
{
th = Convert.ToDouble(r[f[i].Name]);
}
}
try { f[i].SetValue(o, th); }
catch (Exception e1)
{
throw new Exception("can't convert " + f[i].Name + " to doube - value =" + th);
}
break;
case "System.Boolean":
f[i].SetValue(o, Convert.ToInt32(r[f[i].Name]) == 1 ? true : false);
break;
case "System.DateTime":
f[i].SetValue(o, Convert.ToDateTime(r[f[i].Name]));
break;
default:
throw new Exception("Missed data type in sql select in getClassMembers class line 73");
}
}
ret.Add(o);
}
return ret.ToArray();
}
And on and on. You can use reflection like this to create tables that match your class, create insert or procedure calls automatically, and never use an incorrect data type or get a field out of order again.

EPPlus - Read Excel Table

Using EPPlus, I want to read an excel table, then store all the contents from each column into its corresponding List. I want it to recognize the table's heading and categorize the contents based on that.
For example, if my excel table is as below:
Id Name Gender
1 John Male
2 Maria Female
3 Daniel Unknown
I want the data to store in List<ExcelData> where
public class ExcelData
{
public string Id { get; set; }
public string Name { get; set; }
public string Gender { get; set; }
}
So that I can call out the contents using the heading name. For example, when I do this:
foreach (var data in ThatList)
{
Console.WriteLine(data.Id + data.Name + data.Gender);
}
It will give me this output:
1JohnMale
2MariaFemale
3DanielUnknown
This is really all I got:
var package = new ExcelPackage(new FileInfo(#"C:\ExcelFile.xlsx"));
ExcelWorksheet sheet = package.Workbook.Worksheets[1];
var table = sheet.Tables.First();
table.Columns.Something //I guess I can use this to do what I want
Please help :(
I have spent long hours searching for sample code regarding this so that I can learn from it but to no avail. I also understand ExcelToLinQ is managed to do that but it can't recognize table.

Not sure why but none of the above solution work for me.
So sharing what worked:
public void readXLS(string FilePath)
{
FileInfo existingFile = new FileInfo(FilePath);
using (ExcelPackage package = new ExcelPackage(existingFile))
{
//get the first worksheet in the workbook
ExcelWorksheet worksheet = package.Workbook.Worksheets[1];
int colCount = worksheet.Dimension.End.Column; //get Column Count
int rowCount = worksheet.Dimension.End.Row; //get row count
for (int row = 1; row <= rowCount; row++)
{
for (int col = 1; col <= colCount; col++)
{
Console.WriteLine(" Row:" + row + " column:" + col + " Value:" + worksheet.Cells[row, col].Value?.ToString().Trim());
}
}
}
}

There is no native but what if you use what I put in this post:
How to parse excel rows back to types using EPPlus
If you want to point it at a table only it will need to be modified. Something like this should do it:
public static IEnumerable<T> ConvertTableToObjects<T>(this ExcelTable table) where T : new()
{
//DateTime Conversion
var convertDateTime = new Func<double, DateTime>(excelDate =>
{
if (excelDate < 1)
throw new ArgumentException("Excel dates cannot be smaller than 0.");
var dateOfReference = new DateTime(1900, 1, 1);
if (excelDate > 60d)
excelDate = excelDate - 2;
else
excelDate = excelDate - 1;
return dateOfReference.AddDays(excelDate);
});
//Get the properties of T
var tprops = (new T())
.GetType()
.GetProperties()
.ToList();
//Get the cells based on the table address
var start = table.Address.Start;
var end = table.Address.End;
var cells = new List<ExcelRangeBase>();
//Have to use for loops insteadof worksheet.Cells to protect against empties
for (var r = start.Row; r <= end.Row; r++)
for (var c = start.Column; c <= end.Column; c++)
cells.Add(table.WorkSheet.Cells[r, c]);
var groups = cells
.GroupBy(cell => cell.Start.Row)
.ToList();
//Assume the second row represents column data types (big assumption!)
var types = groups
.Skip(1)
.First()
.Select(rcell => rcell.Value.GetType())
.ToList();
//Assume first row has the column names
var colnames = groups
.First()
.Select((hcell, idx) => new { Name = hcell.Value.ToString(), index = idx })
.Where(o => tprops.Select(p => p.Name).Contains(o.Name))
.ToList();
//Everything after the header is data
var rowvalues = groups
.Skip(1) //Exclude header
.Select(cg => cg.Select(c => c.Value).ToList());
//Create the collection container
var collection = rowvalues
.Select(row =>
{
var tnew = new T();
colnames.ForEach(colname =>
{
//This is the real wrinkle to using reflection - Excel stores all numbers as double including int
var val = row[colname.index];
var type = types[colname.index];
var prop = tprops.First(p => p.Name == colname.Name);
//If it is numeric it is a double since that is how excel stores all numbers
if (type == typeof(double))
{
if (!string.IsNullOrWhiteSpace(val?.ToString()))
{
//Unbox it
var unboxedVal = (double)val;
//FAR FROM A COMPLETE LIST!!!
if (prop.PropertyType == typeof(Int32))
prop.SetValue(tnew, (int)unboxedVal);
else if (prop.PropertyType == typeof(double))
prop.SetValue(tnew, unboxedVal);
else if (prop.PropertyType == typeof(DateTime))
prop.SetValue(tnew, convertDateTime(unboxedVal));
else
throw new NotImplementedException(String.Format("Type '{0}' not implemented yet!", prop.PropertyType.Name));
}
}
else
{
//Its a string
prop.SetValue(tnew, val);
}
});
return tnew;
});
//Send it back
return collection;
}
Here is a test method:
[TestMethod]
public void Table_To_Object_Test()
{
//Create a test file
var fi = new FileInfo(#"c:\temp\Table_To_Object.xlsx");
using (var package = new ExcelPackage(fi))
{
var workbook = package.Workbook;
var worksheet = workbook.Worksheets.First();
var ThatList = worksheet.Tables.First().ConvertTableToObjects<ExcelData>();
foreach (var data in ThatList)
{
Console.WriteLine(data.Id + data.Name + data.Gender);
}
package.Save();
}
}
Gave this in the console:
1JohnMale
2MariaFemale
3DanielUnknown
Just be careful if you Id field is an number or string in excel since the class is expecting a string.

This is my working version. Note that the resolvers code is not shown but are a spin on my implementation which allows columns to be resolved even though they are named slightly differently in each worksheet.
public static IEnumerable<T> ToArray<T>(this ExcelWorksheet worksheet, List<PropertyNameResolver> resolvers) where T : new()
{
// List of all the column names
var header = worksheet.Cells.GroupBy(cell => cell.Start.Row).First();
// Get the properties from the type your are populating
var properties = typeof(T).GetProperties().ToList();
var start = worksheet.Dimension.Start;
var end = worksheet.Dimension.End;
// Resulting list
var list = new List<T>();
// Iterate the rows starting at row 2 (ie start.Row + 1)
for (int row = start.Row + 1; row <= end.Row; row++)
{
var instance = new T();
for (int col = start.Column; col <= end.Column; col++)
{
object value = worksheet.Cells[row, col].Text;
// Get the column name zero based (ie col -1)
var column = (string)header.Skip(col - 1).First().Value;
// Gets the corresponding property to set
var property = properties.Property(resolvers, column);
try
{
var propertyName = property.PropertyType.IsGenericType
? property.PropertyType.GetGenericArguments().First().FullName
: property.PropertyType.FullName;
// Implement setter code as needed.
switch (propertyName)
{
case "System.String":
property.SetValue(instance, Convert.ToString(value));
break;
case "System.Int32":
property.SetValue(instance, Convert.ToInt32(value));
break;
case "System.DateTime":
if (DateTime.TryParse((string) value, out var date))
{
property.SetValue(instance, date);
}
property.SetValue(instance, FromExcelSerialDate(Convert.ToInt32(value)));
break;
case "System.Boolean":
property.SetValue(instance, (int)value == 1);
break;
}
}
catch (Exception e)
{
// instance property is empty because there was a problem.
}
}
list.Add(instance);
}
return list;
}
// Utility function taken from the above post's inline function.
public static DateTime FromExcelSerialDate(int excelDate)
{
if (excelDate < 1)
throw new ArgumentException("Excel dates cannot be smaller than 0.");
var dateOfReference = new DateTime(1900, 1, 1);
if (excelDate > 60d)
excelDate = excelDate - 2;
else
excelDate = excelDate - 1;
return dateOfReference.AddDays(excelDate);
}

Below code will read excel data into a datatable, which is converted to list of datarows.
if (FileUpload1.HasFile)
{
if (Path.GetExtension(FileUpload1.FileName) == ".xlsx")
{
Stream fs = FileUpload1.FileContent;
ExcelPackage package = new ExcelPackage(fs);
DataTable dt = new DataTable();
dt= package.ToDataTable();
List<DataRow> listOfRows = new List<DataRow>();
listOfRows = dt.AsEnumerable().ToList();
}
}
using OfficeOpenXml;
using System.Data;
using System.Linq;
public static class ExcelPackageExtensions
{
public static DataTable ToDataTable(this ExcelPackage package)
{
ExcelWorksheet workSheet = package.Workbook.Worksheets.First();
DataTable table = new DataTable();
foreach (var firstRowCell in workSheet.Cells[1, 1, 1, workSheet.Dimension.End.Column])
{
table.Columns.Add(firstRowCell.Text);
}
for (var rowNumber = 2; rowNumber <= workSheet.Dimension.End.Row; rowNumber++)
{
var row = workSheet.Cells[rowNumber, 1, rowNumber, workSheet.Dimension.End.Column];
var newRow = table.NewRow();
foreach (var cell in row)
{
newRow[cell.Start.Column - 1] = cell.Text;
}
table.Rows.Add(newRow);
}
return table;
}
}

Yet another way to do it.
I used Ernie S solution but it didn't work if I had empty cells in the first data row (it wasn't able to guess the data type from it).
So instead of getting a data type from Excel table I get it from the T parameter class properties using reflection.
/// <summary>
/// Converts table to list of T objects
/// </summary>
/// <typeparam name="T">The type to return</typeparam>
/// <param name="table">Data source</param>
/// <returns>List of T objects</returns>
public static IEnumerable<T> ConvertToObjects<T>(this ExcelTable table) where T : new()
{
ExcelCellAddress start = table.Address.Start;
ExcelCellAddress end = table.Address.End;
List<ExcelRange> cells = new();
for (int r = start.Row; r <= end.Row; r++)
for (int c = start.Column; c <= end.Column; c++)
cells.Add(table.WorkSheet.Cells[r, c]);
List<IGrouping<int, ExcelRange>> allRows = cells
.GroupBy(cell => cell.Start.Row)
.OrderBy(cell => cell.Key)
.ToList();
IEnumerable<PropertyInfo> typeProperties = typeof(T).GetProperties();
IGrouping<int, ExcelRangeBase> header = allRows.First();
Dictionary<PropertyInfo, int> columns = new();
foreach (ExcelRangeBase col in header)
{
string propName = col.GetValue<string>();
PropertyInfo propInfo = typeProperties.FirstOrDefault(x => x.Name.Equals(propName));
if (propInfo != null)
{
columns.Add(propInfo, col.Start.Column);
}
}
IEnumerable<IGrouping<int, ExcelRangeBase>> rows = allRows.Skip(1);
List<T> objects = new();
foreach (IGrouping<int, ExcelRangeBase> row in rows)
{
T obj = new();
foreach (KeyValuePair<PropertyInfo, int> colInfo in columns)
{
ExcelRangeBase col = row.First(x => x.Start.Column == colInfo.Value);
if (col.Value == null)
continue;
object value = Convert.ChangeType(col.Value, Nullable.GetUnderlyingType(colInfo.Key.PropertyType) ?? colInfo.Key.PropertyType);
colInfo.Key.SetValue(obj, value);
}
objects.Add(obj);
}
return objects;
}

I have got an error on the first answer so I have changed some code line.
Please try my new code, it's working for me.
using OfficeOpenXml;
using OfficeOpenXml.Table;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
public static class ImportExcelReader
{
public static List<T> ImportExcelToList<T>(this ExcelWorksheet worksheet) where T : new()
{
//DateTime Conversion
Func<double, DateTime> convertDateTime = new Func<double, DateTime>(excelDate =>
{
if (excelDate < 1)
{
throw new ArgumentException("Excel dates cannot be smaller than 0.");
}
DateTime dateOfReference = new DateTime(1900, 1, 1);
if (excelDate > 60d)
{
excelDate = excelDate - 2;
}
else
{
excelDate = excelDate - 1;
}
return dateOfReference.AddDays(excelDate);
});
ExcelTable table = null;
if (worksheet.Tables.Any())
{
table = worksheet.Tables.FirstOrDefault();
}
else
{
table = worksheet.Tables.Add(worksheet.Dimension, "tbl" + ShortGuid.NewGuid().ToString());
ExcelAddressBase newaddy = new ExcelAddressBase(table.Address.Start.Row, table.Address.Start.Column, table.Address.End.Row + 1, table.Address.End.Column);
//Edit the raw XML by searching for all references to the old address
table.TableXml.InnerXml = table.TableXml.InnerXml.Replace(table.Address.ToString(), newaddy.ToString());
}
//Get the cells based on the table address
List<IGrouping<int, ExcelRangeBase>> groups = table.WorkSheet.Cells[table.Address.Start.Row, table.Address.Start.Column, table.Address.End.Row, table.Address.End.Column]
.GroupBy(cell => cell.Start.Row)
.ToList();
//Assume the second row represents column data types (big assumption!)
List<Type> types = groups.Skip(1).FirstOrDefault().Select(rcell => rcell.Value.GetType()).ToList();
//Get the properties of T
List<PropertyInfo> modelProperties = new T().GetType().GetProperties().ToList();
//Assume first row has the column names
var colnames = groups.FirstOrDefault()
.Select((hcell, idx) => new
{
Name = hcell.Value.ToString(),
index = idx
})
.Where(o => modelProperties.Select(p => p.Name).Contains(o.Name))
.ToList();
//Everything after the header is data
List<List<object>> rowvalues = groups
.Skip(1) //Exclude header
.Select(cg => cg.Select(c => c.Value).ToList()).ToList();
//Create the collection container
List<T> collection = new List<T>();
foreach (List<object> row in rowvalues)
{
T tnew = new T();
foreach (var colname in colnames)
{
//This is the real wrinkle to using reflection - Excel stores all numbers as double including int
object val = row[colname.index];
Type type = types[colname.index];
PropertyInfo prop = modelProperties.FirstOrDefault(p => p.Name == colname.Name);
//If it is numeric it is a double since that is how excel stores all numbers
if (type == typeof(double))
{
//Unbox it
double unboxedVal = (double)val;
//FAR FROM A COMPLETE LIST!!!
if (prop.PropertyType == typeof(int))
{
prop.SetValue(tnew, (int)unboxedVal);
}
else if (prop.PropertyType == typeof(double))
{
prop.SetValue(tnew, unboxedVal);
}
else if (prop.PropertyType == typeof(DateTime))
{
prop.SetValue(tnew, convertDateTime(unboxedVal));
}
else if (prop.PropertyType == typeof(string))
{
prop.SetValue(tnew, val.ToString());
}
else
{
throw new NotImplementedException(string.Format("Type '{0}' not implemented yet!", prop.PropertyType.Name));
}
}
else
{
//Its a string
prop.SetValue(tnew, val);
}
}
collection.Add(tnew);
}
return collection;
}
}
How to call this function? please view below code;
private List<FundraiserStudentListModel> GetStudentsFromExcel(HttpPostedFileBase file)
{
List<FundraiserStudentListModel> list = new List<FundraiserStudentListModel>();
if (file != null)
{
try
{
using (ExcelPackage package = new ExcelPackage(file.InputStream))
{
ExcelWorkbook workbook = package.Workbook;
if (workbook != null)
{
ExcelWorksheet worksheet = workbook.Worksheets.FirstOrDefault();
if (worksheet != null)
{
list = worksheet.ImportExcelToList<FundraiserStudentListModel>();
}
}
}
}
catch (Exception err)
{
//save error log
}
}
return list;
}
FundraiserStudentListModel here:
public class FundraiserStudentListModel
{
public string Name { get; set; }
public string Email { get; set; }
public string Phone { get; set; }
}

Working solution with validate email,mobile number
public class ExcelProcessing
{
public List<ExcelUserData> ReadExcel()
{
string path = Config.folderPath + #"\MemberUploadFormat.xlsx";
using (var excelPack = new ExcelPackage())
{
//Load excel stream
using (var stream = File.OpenRead(path))
{
excelPack.Load(stream);
}
//Lets Deal with first worksheet.(You may iterate here if dealing with multiple sheets)
var ws = excelPack.Workbook.Worksheets[0];
List<ExcelUserData> userList = new List<ExcelUserData>();
int colCount = ws.Dimension.End.Column; //get Column Count
int rowCount = ws.Dimension.End.Row;
for (int row = 2; row <= rowCount; row++) // start from to 2 omit header
{
bool IsValid = true;
ExcelUserData _user = new ExcelUserData();
for (int col = 1; col <= colCount; col++)
{
if (col == 1)
{
_user.FirstName = ws.Cells[row, col].Value?.ToString().Trim();
if (string.IsNullOrEmpty(_user.FirstName))
{
_user.ErrorMessage += "Enter FirstName <br/>";
IsValid = false;
}
}
else if (col == 2)
{
_user.Email = ws.Cells[row, col].Value?.ToString().Trim();
if (string.IsNullOrEmpty(_user.Email))
{
_user.ErrorMessage += "Enter Email <br/>";
IsValid = false;
}
else if (!IsValidEmail(_user.Email))
{
_user.ErrorMessage += "Invalid Email Address <br/>";
IsValid = false;
}
}
else if (col ==3)
{
_user.MobileNo = ws.Cells[row, col].Value?.ToString().Trim();
if (string.IsNullOrEmpty(_user.MobileNo))
{
_user.ErrorMessage += "Enter Mobile No <br/>";
IsValid = false;
}
else if (_user.MobileNo.Length != 10)
{
_user.ErrorMessage += "Invalid Mobile No <br/>";
IsValid = false;
}
}
else if (col == 4)
{
_user.IsAdmin = ws.Cells[row, col].Value?.ToString().Trim();
if (string.IsNullOrEmpty(_user.IsAdmin))
{
_user.IsAdmin = "0";
}
}
_user.IsValid = IsValid;
}
userList.Add(_user);
}
return userList;
}
}
public static bool IsValidEmail(string email)
{
Regex regex = new Regex(#"^([a-zA-Z0-9_\-\.]+)#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$",
RegexOptions.CultureInvariant | RegexOptions.Singleline);
return regex.IsMatch(email);
}
}

With this code you won't get an error because a cell is null. it will also cast the data type according to the properties in your class!
using System;
using System.Collections.Generic;
using System.Data;
using System.Data.OleDb;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection;
using OfficeOpenXml;
public static class ReadExcel
{
public static List<T> ReadExcelToList<T>(this ExcelWorksheet worksheet) where T : new()
{
List<T> collection = new List<T>();
try
{
DataTable dt = new DataTable();
foreach (var firstRowCell in new T().GetType().GetProperties().ToList())
{
//Add table colums with properties of T
dt.Columns.Add(firstRowCell.Name);
}
for (int rowNum = 2; rowNum <= worksheet.Dimension.End.Row; rowNum++)
{
var wsRow = worksheet.Cells[rowNum, 1, rowNum, worksheet.Dimension.End.Column];
DataRow row = dt.Rows.Add();
foreach (var cell in wsRow)
{
row[cell.Start.Column - 1] = cell.Text;
}
}
//Get the colums of table
var columnNames = dt.Columns.Cast<DataColumn>().Select(c => c.ColumnName).ToList();
//Get the properties of T
List<PropertyInfo> properties = new T().GetType().GetProperties().ToList();
collection = dt.AsEnumerable().Select(row =>
{
T item = Activator.CreateInstance<T>();
foreach (var pro in properties)
{
if (columnNames.Contains(pro.Name) || columnNames.Contains(pro.Name.ToUpper()))
{
PropertyInfo pI = item.GetType().GetProperty(pro.Name);
pro.SetValue(item, (row[pro.Name] == DBNull.Value) ? null : Convert.ChangeType(row[pro.Name], (Nullable.GetUnderlyingType(pI.PropertyType) == null) ? pI.PropertyType : Type.GetType(pI.PropertyType.GenericTypeArguments[0].FullName)));
}
}
return item;
}).ToList();
}
catch (Exception ex)
{
//Save error log
}
return collection;
}
}
How to call this function? please view below code;
public List<Users> GetStudentsFromExcel(HttpPostedFileBase file)
{
List<Users> list = new List<Users>();
if (file != null)
{
try
{
using (ExcelPackage package = new ExcelPackage(file.InputStream))
{
ExcelWorkbook workbook = package.Workbook;
if (workbook != null)
{
ExcelWorksheet worksheet = workbook.Worksheets.FirstOrDefault();
if (worksheet != null)
{
list = worksheet.ReadExcelToList<Users>();
//Your code
}
}
}
}
catch (Exception ex)
{
//Save error log
}
}
return list;
}
public class Users
{
public string Code { get; set; }
public string Name { get; set; }
public string Email { get; set; }
public string Phone { get; set; }
public string Address { get; set; }
public DateTime CreatedAt { get; set; }
}
Hope to help someone!

Print lists in a list to excel, randomly stops printing after 0.5-6 lists. Comexpection 0x800AC472

First of all I have have some codes which is filling some lists of strings, after that it puts all the lists in 1 big list. Now when I want to print those lists in my excel sheets, it stops after pint half of the first list, or stops after print 5 and a half list, and it says: Exception from HRESULT: 0x800AC472.
There are already 30 tabs in the excel doc, so that is not the problem. Feel free to rename this title, Ihad no idea how to call this problem.
This is how I print my lists in excel:
for (int i = 0; i < ListofLists.Count; i++)
{
for (int j = 1; j <= ListofLists[i].Count; j++)
{
excelDataHandler.excel_setValue("A" + j, ListofLists[i][j-1], "", (i+1));
//A = cell, data of list, color of cell, sheetnumber
}
}
excel_setValue method:
public void excel_setValue(string cellname, string value, string color, int workSheet)
{
((Microsoft.Office.Interop.Excel._Worksheet)newWorkbook_First.Sheets[workSheet]).get_Range(cellname).set_Value(Type.Missing, value);
if (color == "red")
{
newSheets.get_Range(cellname).Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red);
}
}
I would appriciate any help with this problem. Thanks in asvance!

Here is my reflection code.
public static DataTable ClassToDataTable<T>() where T : class
{
Type classType = typeof(T);
List<PropertyInfo> propertyList = classType.GetProperties().ToList();
if (propertyList.Count < 1)
{
return new DataTable();
}
string className = classType.UnderlyingSystemType.Name;
DataTable result = new DataTable(className);
foreach (PropertyInfo property in propertyList)
{
DataColumn col = new DataColumn();
col.ColumnName = property.Name;
Type dataType = property.PropertyType;
if (IsNullable(dataType))
{
if (dataType.IsGenericType)
{
dataType = dataType.GenericTypeArguments.FirstOrDefault();
}
}
else
{ // True by default
col.AllowDBNull = false;
}
col.DataType = dataType;
result.Columns.Add(col);
}
return result;
}
public static DataTable ClassListToDataTable<T>(List<T> ClassList) where T : class
{
DataTable result = ClassToDataTable<T>();
if (result.Columns.Count < 1)
{
return new DataTable();
}
if (ClassList.Count < 1)
{
return result;
}
foreach (T item in ClassList)
{
ClassToDataRow(ref result, item);
}
return result;
}
public static void ClassToDataRow<T>(ref DataTable Table, T Data) where T : class
{
Type classType = typeof(T);
string className = classType.UnderlyingSystemType.Name;
// Checks that the table name matches the name of the class.
// There is not required, and it may be desirable to disable this check.
// Comment this out or add a boolean to the parameters to disable this check.
if (!Table.TableName.Equals(className))
{
return;
}
DataRow row = Table.NewRow();
List<PropertyInfo> propertyList = classType.GetProperties().ToList();
foreach (PropertyInfo prop in propertyList)
{
if (Table.Columns.Contains(prop.Name))
{
if (Table.Columns[prop.Name] != null)
{
row[prop.Name] = prop.GetValue(Data, null);
}
}
}
Table.Rows.Add(row);
}
public static bool IsNullable(Type Input)
{
if (!Input.IsValueType) return true; // Is a ref-type, such as a class
if (Nullable.GetUnderlyingType(Input) != null) return true; // Nullable
return false; // Must be a value-type
}

How to convert a list into data table [duplicate]

This question already has answers here:
Convert generic List/Enumerable to DataTable?
(28 answers)
Closed 9 years ago.
I have a data list with some property. I want to convert that list data into data table. How to convert a list into datable.

Add this function and call it, it will convert List to DataTable.
public static DataTable ToDataTable<T>(List<T> items)
{
DataTable dataTable = new DataTable(typeof(T).Name);
//Get all the properties
PropertyInfo[] Props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (PropertyInfo prop in Props)
{
//Defining type of data column gives proper data table
var type = (prop.PropertyType.IsGenericType && prop.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>) ? Nullable.GetUnderlyingType(prop.PropertyType) : prop.PropertyType);
//Setting column names as Property names
dataTable.Columns.Add(prop.Name, type);
}
foreach (T item in items)
{
var values = new object[Props.Length];
for (int i = 0; i < Props.Length; i++)
{
//inserting property values to datatable rows
values[i] = Props[i].GetValue(item, null);
}
dataTable.Rows.Add(values);
}
//put a breakpoint here and check datatable
return dataTable;
}

you can use this extension method and call it like this.
DataTable dt = YourList.ToDataTable();
public static DataTable ToDataTable<T>(this List<T> iList)
{
DataTable dataTable = new DataTable();
PropertyDescriptorCollection propertyDescriptorCollection =
TypeDescriptor.GetProperties(typeof(T));
for (int i = 0; i < propertyDescriptorCollection.Count; i++)
{
PropertyDescriptor propertyDescriptor = propertyDescriptorCollection[i];
Type type = propertyDescriptor.PropertyType;
if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
type = Nullable.GetUnderlyingType(type);
dataTable.Columns.Add(propertyDescriptor.Name, type);
}
object[] values = new object[propertyDescriptorCollection.Count];
foreach (T iListItem in iList)
{
for (int i = 0; i < values.Length; i++)
{
values[i] = propertyDescriptorCollection[i].GetValue(iListItem);
}
dataTable.Rows.Add(values);
}
return dataTable;
}

private DataTable CreateDataTable(IList<T> item)
{
Type type = typeof(T);
var properties = type.GetProperties();
DataTable dataTable = new DataTable();
foreach (PropertyInfo info in properties)
{
dataTable.Columns.Add(new DataColumn(info.Name, Nullable.GetUnderlyingType(info.PropertyType) ?? info.PropertyType));
}
foreach (T entity in item)
{
object[] values = new object[properties.Length];
for (int i = 0; i < properties.Length; i++)
{
values[i] = properties[i].GetValue(entity);
}
dataTable.Rows.Add(values);
}
return dataTable;
}

Which way is the best for removing duplicates from a dataTable with multiple columns

Which way is the best for removing duplicates from a dataTable for multiple columns?I mean below code is only for a single column.
public DataTable RemoveDuplicateRows(DataTable dTable, string colName)
{
Hashtable hTable = new Hashtable();
ArrayList duplicateList = new ArrayList();
//Add list of all the unique item value to hashtable, which stores combination of key, value pair.
//And add duplicate item value in arraylist.
foreach (DataRow drow in dTable.Rows)
{
if (hTable.Contains(drow[colName]))
duplicateList.Add(drow);
else
hTable.Add(drow[colName], string.Empty);
}
//Removing a list of duplicate items from datatable.
foreach (DataRow dRow in duplicateList)
dTable.Rows.Remove(dRow);
//Datatable which contains unique records will be return as output.
return dTable;
}
I tried using string[] colName. It throws error at dTable.Rows.Remove(dRow);
Please suggest.

The easiest and most readable is using Linq-to-DataTable:
var groups = from r in dTable.AsEnumerable()
group r by new
{
Col1 = r.Field<String>("Column1"),
Col2 = r.Field<String>("Column2"),
};
// if you only want the first row of each group:
DataTable distinctTable = groups.Select(g => g.First()).CopyToDataTable();
Notes: Enumerable.GroupBy groups the DataRows by an anonymous type with two properties(Col1 and Col2) which are initialized from a DataRow fields Column1 and Column2.
So you get groups of IEnumerable<DataRow>. Enumerable.First() returns the first DataRow of each group (you could also use different methods to select the row you want to keep, for example by ordering by a date field).
Then CopyToDataTable creates a new DataTable from the (now) distinct DataRows.
Here's a possible implementation if you're using .NET 2:
implementation of a custom IEqualityComparer<Object[]> for the dictionary:
class ObjectArrayComparer : IEqualityComparer<Object[]>
{
public bool Equals(Object[] x, Object[] y)
{
if (x == null && y == null) return true;
if (x == null || y == null) return false;
if (x.Length != y.Length) return false;
for (int i = 0; i < x.Length; i++)
{
if (x[i] == null && y[i] == null) continue;
if (x[i] == null || y[i] == null) return false;
if (!x[i].Equals(y[i])) return false;
}
return true;
}
public int GetHashCode(Object[] obj)
{
int hash = 0;
if (obj != null)
{
hash = (hash * 17) + obj.Length;
foreach (Object o in obj)
{
hash *= 17;
if (o != null) hash = hash + o.GetHashCode();
}
}
return hash;
}
}
your RemoveDuplicateRows method:
public DataTable RemoveDuplicateRows(DataTable dTable, String[] colNames)
{
var hTable = new Dictionary<object[], DataRow>(new ObjectArrayComparer());
foreach (DataRow drow in dTable.Rows)
{
Object[] objects = new Object[colNames.Length];
for (int c = 0; c < colNames.Length; c++)
objects[c] = drow[colNames[c]];
if (!hTable.ContainsKey(objects))
hTable.Add(objects, drow);
}
// create a clone with the same columns and import all distinct rows
DataTable clone = dTable.Clone();
foreach (var kv in hTable)
clone.ImportRow(kv.Value);
return clone;
}
testing:
var table = new DataTable();
table.Columns.Add("Colum1", typeof(string));
table.Columns.Add("Colum2", typeof(int));
table.Columns.Add("Colum3", typeof(string));
Random r = new Random();
for (int i = 0; i < 100; i++)
{
table.Rows.Add("Colum1_" + r.Next(1, 10), r.Next(1, 10), "Colum3_" + r.Next(1, 10));
}
int rowCount = table.Rows.Count; // 100
var unique = RemoveDuplicateRows(table, new[] { "Colum1", "Colum2" });
int uniqueRowCount = unique.Rows.Count; // around 55-65

You can use Distinct on Datatable.Select ... Link
Refer this Link

Below is your code with several amends of mine.
The main idea is to add to HashTable(Dictionary<> in my code) not value of only one column but values of specified columns and threat them these several values in atomic way(like single one).
// your code with minor amends
public DataTable RemoveDuplicateRows(DataTable dTable, string[] colNames)
{
// note that strongly typed dictionary has replaced the hash table + it uses custom comparer
var hTable = new Dictionary<DataRowInfo, string>();
var duplicateList = new ArrayList();
//Add list of all the unique item value to hashtable, which stores combination of key, value pair.
//And add duplicate item value in arraylist.
foreach (DataRow drow in dTable.Rows)
{
var dataRowInfo = new DataRowInfo(drow, colNames);
if (hTable.ContainsKey(dataRowInfo))
duplicateList.Add(drow);
else
hTable.Add(dataRowInfo, string.Empty);
}
//Removing a list of duplicate items from datatable.
foreach (DataRow dRow in duplicateList)
dTable.Rows.Remove(dRow);
//Datatable which contains unique records will be return as output.
return dTable;
}
// Helper classes
// contains values of specified columns
internal sealed class DataRowInfo
{
public object[] Values { get; private set; }
public DataRowInfo(DataRow dataRow, string[] columns)
{
Values = columns.Select(c => dataRow[c]).ToArray();
}
public override bool Equals(object obj)
{
if (ReferenceEquals(this, obj))
return true;
var other = obj as DataRowInfo;
if (other == null)
return false;
return Equals(other);
}
private bool Equals(DataRowInfo other)
{
if (this.Values.Length != other.Values.Length)
return false;
for (int i = 0; i < this.Values.Length; i++)
{
if (AreObjectsEqual(this.Values[i], other.Values[i]))
return false;
}
return true;
}
private static bool AreObjectsEqual(object left, object right)
{
if (ReferenceEquals(left, right))
return true;
if (ReferenceEquals(left, null))
return false;
if (ReferenceEquals(right, null))
return false;
if (left.GetType() != right.GetType())
return false;
return left.Equals(right);
}
public override int GetHashCode()
{
unchecked
{
int hashCode = 0;
foreach (var value in this.Values)
{
hashCode = hashCode ^ ((value != null ? value.GetHashCode() : 0) * 397);
}
return hashCode;
}
}
}
Hope this will help.
UPDATE
Simplified code a bit.