问题
I'm getting values from another data table as input to list. Now i need to save those list values into another DataTable.
List:
List<DataRow> list = slectedFieldsTable.AsEnumerable().ToList();
foreach (DataRow dr in slectedFieldsTable.Rows)
{
list.Add(dr);
}
New Data table :
DataRow newRow = tempTable.NewRow();
newRow["Field Name"] = fieldLabel;
newRow["Field Type"] = fieldType;
for(int gg =0 ; gg<list.Count; gg++)
{
tempTable.Rows.Add(????);
}
I'm stuck here in adding up rows in to new data table.
回答1:
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)
{
//Setting column names as Property names
dataTable.Columns.Add(prop.Name);
}
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;
}
回答2:
Variable declare:
DataTable tempTable = new DataTable();
DataTable slectedFieldsTable = new DataTable();
DataRow newRow;
List<object> list = new List<object>();
Add Column in DataTable:
slectedFieldsTable = new DataTable();
slectedFieldsTable.Columns.Add("Field Name");
slectedFieldsTable.Columns.Add("Field Type");
Add Value in DataTable:
slectedFieldsTable.Rows.Add("1", "AAA");
slectedFieldsTable.Rows.Add("2", "BBB");
slectedFieldsTable.Rows.Add("3", "CCC");
Convert DataTable to List:
foreach (DataRow dr in slectedFieldsTable.Rows)
{
list.Add(dr);
}
Add Column in another DataTable:
tempTable.Columns.Add("Field Name", typeof(string));
tempTable.Columns.Add("Field Type", typeof(string));
Convert List to dataTable:
foreach(DataRow dr in list)
{
newRow = tempTable.NewRow();
newRow["Field Name"] = dr.ItemArray[0].ToString();
newRow["Field Type"] = dr.ItemArray[1].ToString();
tempTable.Rows.Add(newRow);
tempTable.AcceptChanges();
}
回答3:
use CopyToDataTable() method. CopyToDataTable
IEnumerable<DataRow> query = TempselectedFieldsTable.AsEnumerable().ToList();
// Create a table from the query.
DataTable boundTable = query.CopyToDataTable<DataRow>();
回答4:
Try this:
foreach (DataRow dr in list)
{
tempTable.Rows.Add(dr);
}
回答5:
The answer providing the ToDataTable is a very nice start but it is missing some key elements. Namely, it ignores that List item properties may:
- ...be marked
ReadOnly - ...use the
DisplayNameattribute - ...have a
DefaultValuewhich theDataColumnshould know about - ...be
Nullable - ...be marked
BrowsableAttribute(false)
The following is an extension method to return a DataTable and either accounts for the above or provides the means for your code to apply them. It also uses an Interface to get the values from the class object rather than Reflection.
public static DataTable ToDataTable<T>(this IList<T> lst, bool includeAll = true)
{
DataTable dt = new DataTable();
DataColumn dc;
PropertyDescriptor pd;
bool Browsable;
PropertyDescriptorCollection propCol = TypeDescriptor.GetProperties(typeof(T));
for (int n = 0; n < propCol.Count; n++)
{
pd = propCol[n];
Type propT = pd.PropertyType;
dc = new DataColumn(pd.Name);
// if Nullable, get underlying type
// the first test may not be needed
if (propT.IsGenericType && Nullable.GetUnderlyingType(propT) != null )
{
propT = Nullable.GetUnderlyingType(propT);
dc.DataType = propT;
dc.AllowDBNull = true;
}
else
{
dc.DataType = propT;
dc.AllowDBNull = false;
}
// is it readonly?
if (pd.Attributes[typeof(ReadOnlyAttribute)] != null)
{
dc.ReadOnly = ((ReadOnlyAttribute)pd.
Attributes[typeof(ReadOnlyAttribute)]).IsReadOnly;
}
// DefaultValue ...
if (pd.Attributes[typeof(DefaultValueAttribute)] != null)
{
dc.DefaultValue = ((DefaultValueAttribute)pd.
Attributes[typeof(DefaultValueAttribute)]).Value;
}
// caption / display name
dc.ExtendedProperties.Add("DisplayName", dc.Caption);
if (pd.Attributes[typeof(DisplayNameAttribute)] != null)
{
// these are usually present but blank
string theName = ((DisplayNameAttribute)pd.
Attributes[typeof(DisplayNameAttribute)]).DisplayName;
dc.Caption = string.IsNullOrEmpty(theName) ? dc.Caption : theName;
// DGV doesnt use Caption...save for later
dc.ExtendedProperties["DisplayName"] = dc.Caption;
}
Browsable = true;
dc.ExtendedProperties.Add("Browsable", Browsable);
var foo = pd.Attributes[typeof(BrowsableAttribute)];
if (pd.Attributes[typeof(BrowsableAttribute)] != null)
{
Browsable = ((BrowsableAttribute)pd.Attributes[typeof(BrowsableAttribute)]).Browsable;
// no such thing as a NonBrowsable DataColumn
dc.ExtendedProperties["Browsable"] = Browsable;
}
// ToDo: add support for custom attributes
if (includeAll || Browsable)
{
dt.Columns.Add(dc);
}
}
// the lst could be empty such as creating a typed table
if (lst.Count == 0) return dt;
if (lst[0] is IDataValuesProvider)
{
IDataValuesProvider dvp;
// copy the data - let the class do the work
foreach (T item in lst)
{
dvp = (IDataValuesProvider)item;
dt.Rows.Add(dvp.GetDataValues(includeAll).ToArray());
}
}
else
{
List<object> values;
foreach (T item in lst)
{
values = new List<object>();
// only Browsable columns added
for (int n = 0; n < dt.Columns.Count; n++)
{
values.Add(propCol[dt.Columns[n].ColumnName].GetValue(item));
}
dt.Rows.Add(values.ToArray());
}
}
return dt;
}
The method allows you to specify whether columns for non Browsable properties should be added to the DataTable. Rather than hiding the columns later, you can omit them entirely if you want.
An interface proves the means to get the data values from collection members in order (as an alternative to a reflection loop):
public interface IDataValuesProvider
{
IEnumerable<object> GetDataValues(bool includeAll);
}
... on the class:
public class StockItem : IDataValuesProvider
{
public int Id { get; set; }
public string ItemName {get; set;}
[Browsable(false), DisplayName("Ignore")]
public string propA {get; set;}
[ReadOnly(true)]
public string Zone { get; set; }
public string Size {get; set;}
[DisplayName("Nullable")]
public int? Foo { get; set; }
public int OnHand {get; set;}
public string ProdCode {get; set;}
[Browsable(false)]
public string propB { get; set; }
public DateTime ItemDate {get; set;}
// IDataValuesProvider implementation
public IEnumerable<object> GetDataValues(bool IncludeAll)
{
List<object> values = new List<object>();
values.AddRange(new object[] {Id, ItemName });
if (IncludeAll) values.Add(propA);
values.AddRange(new object[] { Zone, Size, Foo, OnHand, ProdCode });
if (IncludeAll) values.Add(propB);
values.Add(ItemDate);
return values;
}
}
Add the data values in the same order as they are listed in your class; be sure to update it when you add properties. The reflection version is still there so you can do it either way.
Finally, there are a few common Attributes which do not have a related DataColumn property. The method stores these for you as ExtendedProperties allowing you to easily apply them to the DGV:
var dtX = someData.ToDataTable();
dgvB.SuspendLayout();
dgvB.DataSource = dtX;
// process extended props
foreach (DataColumn dc in dtX.Columns)
{
// no need to test, the code adds them everytime
//if (dc.ExtendedProperties.ContainsKey("DisplayName"))
//{
dgvB.Columns[dc.ColumnName].HeaderText = dc.ExtendedProperties["DisplayName"].ToString();
//}
//if (dc.ExtendedProperties.ContainsKey("Browsable"))
//{
dgvB.Columns[dc.ColumnName].Visible = (bool)dc.ExtendedProperties["Browsable"];
//}
}
dgvB.ResumeLayout();
Results using a list of the class shown above:
Both OnHand and Foo show the DisplayName and both PropA and PropB are hidden. Most importantly, columns created for ReadOnly and Nullable properties act accordingly.
来源：https://stackoverflow.com/questions/15128140/how-to-convert-a-list-into-datatable