This method is to convert the list to a DataTable. I commented the code for you understanding.
public static DataTable ToDataTable<T>(this List<T> iList)
{
DataTable dataTable = new DataTable();
//Creates a new collection and assign it the properties for typeof(T)
PropertyDescriptorCollection propertyDescriptorCollection = TypeDescriptor.GetProperties(typeof(T));
//Traverse this collection
for (int i = 0; i < propertyDescriptorCollection.Count; i++)
{
//Set the PropertyDescriptor
PropertyDescriptor propertyDescriptor = propertyDescriptorCollection[i];
//Get the type of the property
Type type = propertyDescriptor.PropertyType;
//type.IsGenericType represent the current type is a generic type
//type.GetGenericTypeDefinition() return a Type object that represents a generic type definition from which the current generic type can be constructed
//Nullable<> represent a value type that can be assigned null
if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
type = Nullable.GetUnderlyingType(type); //Return the underlying type argument of the specified nullable type.
dataTable.Columns.Add(propertyDescriptor.Name, type); // add propertyDescriptor.Name as the table column name
}
//Define an array
object[] values = new object[propertyDescriptorCollection.Count];
foreach (T iListItem in iList)
{
for (int i = 0; i < values.Length; i++)
{
//Assign the value of the collection propertyDescriptorCollection to value
values[i] = propertyDescriptorCollection[i].GetValue(iListItem);
}
dataTable.Rows.Add(values); //add the values as the table value
}
return dataTable;
}
jsshivalik
how i can call this by passing Sql Query
Can you tell me why call this method by passing sql query? what is its application scenario?
Best regards,
Sam
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As PatriceSc said, using adapter can meet your needs.
private static DataTable dt(DataTable datatable,string connectionString, string queryString)
{
using (SqlConnection connection =new SqlConnection(connectionString))
{
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = new SqlCommand(queryString, connection);
adapter.Fill(datatable);
return datatable;
}
}
The above is the sql database. what should note is what database you are using.
Best regards,
Sam
.NET forums are moving to a new home on Microsoft Q&A, we encourage you to go to Microsoft Q&A for .NET for posting new questions and get involved today.
I don't quite understand what you mean. Isn't this a variable that declares a DataTable type?
Best regards,
sam
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Generic List
Sep 28, 2019 05:52 AM|jsshivalik|LINK
Hi
How the below code works & how i can call this by passing Sql Query
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; }Thanks
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Re: Generic List
Sep 30, 2019 08:05 AM|samwu|LINK
Hi jsshivalik,
This method is to convert the list to a DataTable. I commented the code for you understanding.
public static DataTable ToDataTable<T>(this List<T> iList) { DataTable dataTable = new DataTable(); //Creates a new collection and assign it the properties for typeof(T) PropertyDescriptorCollection propertyDescriptorCollection = TypeDescriptor.GetProperties(typeof(T)); //Traverse this collection for (int i = 0; i < propertyDescriptorCollection.Count; i++) { //Set the PropertyDescriptor PropertyDescriptor propertyDescriptor = propertyDescriptorCollection[i]; //Get the type of the property Type type = propertyDescriptor.PropertyType; //type.IsGenericType represent the current type is a generic type //type.GetGenericTypeDefinition() return a Type object that represents a generic type definition from which the current generic type can be constructed //Nullable<> represent a value type that can be assigned null if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>)) type = Nullable.GetUnderlyingType(type); //Return the underlying type argument of the specified nullable type. dataTable.Columns.Add(propertyDescriptor.Name, type); // add propertyDescriptor.Name as the table column name } //Define an array object[] values = new object[propertyDescriptorCollection.Count]; foreach (T iListItem in iList) { for (int i = 0; i < values.Length; i++) { //Assign the value of the collection propertyDescriptorCollection to value values[i] = propertyDescriptorCollection[i].GetValue(iListItem); } dataTable.Rows.Add(values); //add the values as the table value } return dataTable; }Can you tell me why call this method by passing sql query? what is its application scenario?
Best regards,
Sam
Member
140 Points
520 Posts
Re: Generic List
Sep 30, 2019 04:47 PM|jsshivalik|LINK
Hi Samwu
Thank but how i will call this method
Thanks
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Re: Generic List
Sep 30, 2019 05:08 PM|PatriceSc|LINK
Hi,
Which db access API are you using ? Some more context could help.
If you want to fill a DataTable using a SQL query you could use https://docs.microsoft.com/en-us/dotnet/api/system.data.sqlclient.sqldataadapter?view=netframework-4.8 (this code sample uses a DataSet but you can use the same code with a DataTable instead).
Or do you really want to use for example Entity Framework to fill a list of objects and then fill a DataTable from this list?
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Re: Generic List
Sep 30, 2019 06:23 PM|mgebhard|LINK
The shared snippet is part of an extension method pattern (it's missing the class) that converts a List<T> into a DataTable.
Implementation would look similar to the following.
List<MyType> items = datalayer.getMyItems(); DataTable dt = items.ToDataTable();Extension method reference.
https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods
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Re: Generic List
Oct 01, 2019 01:43 AM|samwu|LINK
Hi jsshivalik,
As PatriceSc said, using adapter can meet your needs.
private static DataTable dt(DataTable datatable,string connectionString, string queryString) { using (SqlConnection connection =new SqlConnection(connectionString)) { SqlDataAdapter adapter = new SqlDataAdapter(); adapter.SelectCommand = new SqlCommand(queryString, connection); adapter.Fill(datatable); return datatable; } }The above is the sql database. what should note is what database you are using.
Best regards,
Sam
Member
140 Points
520 Posts
Re: Generic List
Oct 01, 2019 04:39 AM|jsshivalik|LINK
Hi Samwu
With this i can use only Sql Database . Suppose some other Database is used at later stage then this code may not work.
Secondly how DataTable datatables works
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Re: Generic List
Oct 01, 2019 05:28 AM|samwu|LINK
Hi jsshivalik,
Other databases are similarly written. you can refer to this link:
https://docs.microsoft.com/en-us/dotnet/api/system.data.oledb.oledbdataadapter?view=netframework-4.8
I don't quite understand what you mean. Isn't this a variable that declares a DataTable type?
Best regards,
sam