How to add CsvHelper records to DataTable to use for SqlBulkCopy to the database

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有刺的猬
有刺的猬 2021-02-14 08:18

I am trying to read a CSV file with CsvHelper, load each record into a DataTable, and then use SqlBulkCopy to insert the data into a database table. With the current code, I get

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  • 2021-02-14 09:03

    Josh added support to read headers last year and the following block may be useful to those who just want to build a DataTable using the schema of the CSV document. I wanted to post this as a comment to Josh's answer as it is only a small modification but posting as an answer as I couldn't format a code block in Comments.

        private DataTable BuildDataTable()
        {
            var dt = new DataTable();
    
            using (var textReader = new StreamReader(_path))
            {
                using (var csv = new CsvReader(textReader))
                {
                    csv.ReadHeader();
                    foreach (var header in csv.FieldHeaders)
                    {
                        dt.Columns.Add(header);
                    }
    
    
                    while (csv.Read())
                    {
                        var row = dt.NewRow();
                        foreach (DataColumn column in dt.Columns)
                        {
                            row[column.ColumnName] = csv.GetField(column.DataType, column.ColumnName);
                        }
                        dt.Rows.Add(row);
                    }
                }
            }
    
            return dt;
        }
    
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  • 2021-02-14 09:09

    If I'm not mistaken, you should be able to do it with a lot less code. You don't have to put in into another class before going into the DataTable either.

    while( csv.Read() )
    {
        var row = dt.NewRow();
        foreach( DataColumn column in dt.Columns )
        {
            row[column.ColumnName] = csv.GetField( column.DataType, column.ColumnName );
        }
        dt.Rows.Add( row );
    }
    
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  • 2021-02-14 09:11

    I was able to get this to work by adding a DataTable row and filling it in explicitly, instead of trying to add a CsvHelper record as a row.

    I used the following part instead of the similar part that is shown above:

    foreach (var record in records)
    {
        DataRow row = dt.NewRow();
        record.CompanyId = company.Id;
        row["Date"] = record.Date;
        row["Close"] = record.Close;
        row["AdjClose"] = record.AdjClose;
        row["High"] = record.High;
        row["Low"] = record.Low;
        row["Open"] = record.Open;
        row["Volume"] = record.Volume;
        row["CompanyId"] = record.CompanyId;
        dt.Rows.Add(row);
    }
    

    If you can solve the issue without so much hard coding, I will accept your answer as the answer.

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  • 2021-02-14 09:20

    I liked the answer from @JoshClose, but I found while( csv.Read() ) to be considerably slower than csv.GetRecords<{Class}>().ToList(). It also doesn't correctly handle many nullable types like int? when the value returned should be DBNull. My answer is to have CsvHelper import a list of dynamic records and then use a couple helper methods to auto map to the DataTable.

    var records = csv.GetRecords<dynamic>().ToList();
    
    foreach ( record in records )
    {
        var row = dt.NewRow();
    
        var recordDictionary = DynamicToDictionary( record );
    
        foreach( DataColumn column in dt.Columns )
        {
            row[column.ColumnName] = GetColumnValue( column, recordDictionary );
        }
    
        dt.Rows.Add( row );
    }
    

    The DynamicToDictionary method handles case sensitivity and header white space. I convert the dynamic object to a Dictionary object that ignores case sensitivity and removes header white space. This could be skipped and the dynamic object passed directly to GetColumnValue if this isn't an issue.

    public Dictionary<string, object> DynamicToDictionary(dynamic dynObj)
    {
        var dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
    
        foreach (var kvp in (IDictionary<string, object>) dynObj)
        {
            var obj = kvp.Value;
    
            // Remove white space.
            var name = new string(kvp.Key.ToCharArray().Where(c => !char.IsWhiteSpace(c)).ToArray());
    
            dictionary.Add(name, obj);
        }
    
        return dictionary;
    }
    

    The GetColumnValue method finds and converts the dynamic record value into the proper DataTable column value.

    public object GetColumnValue(DataColumn column, IDictionary<string, object> dynamicDictionary)
    {
        object value;
    
        // Return DBNull if the column name isn't found.
        if (!dynamicDictionary.TryGetValue(column.ColumnName, out value))
        {
            return DBNull.Value;
        }
    
        // Null values come in as empty strings.
        if (column.AllowDBNull && column.DataType != typeof(string) && (string)value == "")
        {
            return DBNull.Value;
        }
    
        if (column.DataType == typeof(bool))
        {
            return (string)value != "0" && ((string)value).ToLower() != "false";
        }
    
        return value;
    }
    
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