DataSet 不支持导出中的 System.Nullable<>

Question

I was trying to generate a Report using Export to Excell, PDF, TextFile. Well I am doing this in MVC. I have a class which I named SPBatch (which is the exact name of my Stored Procedure in my SQL) and it contains the following:

public string BatchNo { get; set; }
public string ProviderName { get; set; }
public Nullable<System.Int32> NoOfClaims { get; set; }
public Nullable<System.Int32> TotalNoOfClaims { get; set; }
public Nullable<System.Decimal> TotalBilled { get; set; }
public Nullable<System.Decimal> TotalInputtedBill { get; set; }
public Nullable<System.DateTime> DateCreated { get; set; }
public Nullable<System.DateTime> DateSubmitted { get; set; }
public Nullable<System.DateTime> DueDate { get; set; }
public string Status { get; set; }
public string RefNo { get; set; }
public string BatchStatus { get; set; }
public string ClaimType { get; set; }

as you can see some of my Columns are declared as Nullable. It went smoothly from searching and displaying the results in a table. I have several buttons below which are image buttons for export and every time I try to export in Excel, I always get the problem " DataSet does not support System.Nullable<> " in this part of my code:

foreach (MemberInfo mi in miArray)
{
    if (mi.MemberType == MemberTypes.Property)
    {
        PropertyInfo pi = mi as PropertyInfo;
        dt.Columns.Add(pi.Name, pi.PropertyType); //where the error pop's up.

    }
    else if (mi.MemberType == MemberTypes.Field)
    {
        FieldInfo fi = mi as FieldInfo;
        dt.Columns.Add(fi.Name, fi.FieldType);
    }
}

the error shows up on the one with a comment. Can you help me what to do? I tried adding DBNull in my code but still I get the same error. I tried removing Nullable in my SPBatch but I get an error that some tables are need to be declared as Nullable.

What should I do?

Answer 1

try with

dt.Columns.Add(pi.Name, Nullable.GetUnderlyingType(
            pi.PropertyType) ?? pi.PropertyType);

Answer 2

Thanks to a C# version of a generating a datatable and some hacking around, I can offer this answer in VB - I put it on here because I've just had a lot of hassle wanting to get a filterable dataset from a stored proc whilst using a simple datalayer. I hope it helps someone else!

Note: The use case is where you wish to use BindingSource.Filter = "some query string":

Imports System.Reflection

Public Module Extenders
<System.Runtime.CompilerServices.Extension>
Public Function ToDataTable(Of T)(collection As IEnumerable(Of T), tableName As String) As DataTable
    Dim tbl As DataTable = ToDataTable(collection)
    tbl.TableName = tableName
    Return tbl
End Function

<System.Runtime.CompilerServices.Extension>
Public Function ToDataTable(Of T)(collection As IEnumerable(Of T)) As DataTable
    Dim dt As New DataTable()

    Dim tt As Type = GetType(T)
    Dim pia As PropertyInfo() = tt.GetProperties()

    'Create the columns in the DataTable

    For Each pi As PropertyInfo In pia
        Dim a = 
If(Nullable.GetUnderlyingType(pi.PropertyType), pi.PropertyType)
        dt.Columns.Add(pi.Name, If(Nullable.GetUnderlyingType(pi.PropertyType), pi.PropertyType))
    Next

    'Populate the table

    For Each item As T In collection
        Dim dr As DataRow = dt.NewRow()
        dr.BeginEdit()

        For Each pi As PropertyInfo In pia

            dr(pi.Name) = If(Nullable.GetUnderlyingType(pi.PropertyType) Is GetType(DateTime), DBNull.Value, pi.GetValue(item, Nothing))
        Next
        dr.EndEdit()
        dt.Rows.Add(dr)
    Next
    Return dt
End Function

End Module

Answer 3

I would search for nullable and replace it with a string which can be null unlike a DateTime.

foreach (PropertyInfo pi in properties)
{
    if (pi.PropertyType.Name.Contains("Nullable"))
       myDataType = typeof(String);
    else
       myDataType = pi.PropertyType;
}

Here is a complete version:

private DataTable CreateDataTable(PropertyInfo[] properties)
{
    DataTable dt = new DataTable();
    DataColumn dc = null;
    foreach (PropertyInfo pi in properties)
    {
        dc = new DataColumn();
        dc.ColumnName = pi.Name;

        if (pi.PropertyType.Name.Contains("Nullable"))
            dc.DataType = typeof(String);
        else
            dc.DataType = pi.PropertyType;

        // dc.DataType = pi.PropertyType;
        dt.Columns.Add(dc);
    }
    return dt;
}

Answer 4

1) Define This Extensions as Below

public static class ListExtensions
    {
        public static DataTable ToDataTable<T>(this List<T> list)
        {
            DataTable table = new DataTable(typeof(T).Name);

            //Get Properites of List Fiels
            PropertyInfo[] props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

            //Create Columns as Fields of List
            foreach (PropertyInfo propertyInfo in props)
            {
                var column = new DataColumn
                {
                    ColumnName = propertyInfo.Name,
                    DataType = propertyInfo.PropertyType.Name.Contains("Nullable") ? typeof(string) : propertyInfo.PropertyType
                };

                table.Columns.Add(column);
            }

            //Fill DataTable with Rows of List
            foreach (var item in list)
            {
                var values = new object[props.Length];

                for (var i = 0; i < props.Length; i++)
                {
                    values[i] = props[i].GetValue(item, null);
                }

                table.Rows.Add(values);
            }


            return table;
        }
    }

2) Call Extensions Method as Below where [_lstOperationDetails] is List that we want to convert it from List to DataTable

DataTable operationDetails = _lstOperationDetails.ToDataTable();