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Write Object in CSV/Excel File

There are many instance where we need to write an object in to CSV or Excel file, here is a CSVHelper class which will server this purpose.

Below is the a user defined attribute, we need to apply this attribute to the properties which we want to write in Excel file.

    /// <summary>
    /// The name of the column for the CSV
    /// generated by a list of objects with
    /// properties marked with this attribute,
    /// if Export is true.  Uses Order to order
    /// the properties on export
    /// </summary>
    public class CsvColumnNameAttribute : Attribute
    {
        public bool Export { get; set; }
        public int Order { get; set; }
        public string Name { get; set; }

        public CsvColumnNameAttribute()
        {
            Export = true;
            Order = int.MaxValue; // so unordered columns are at the end
        }

    }

Below class have a public generic methods which will be called from client code. It takes the list of object we want to write in the CSV file

    public class CSVHelper
    {
        /// <summary>
        /// Generate a CSV as a string from a list
        /// of objects that have the CsvColumnNameAttribute
        /// applied
        /// </summary>
        public string GetCsv<T>(List<T> csvDataObjects)
        {
            PropertyInfo[] propertyInfos = typeof(T).GetProperties();
            var sb = new StringBuilder();
            sb.AppendLine(GetCsvHeaderSorted(propertyInfos));
            csvDataObjects.ForEach(d => sb.AppendLine(GetCsvDataRowSorted(d, propertyInfos)));
            return sb.ToString();
        }

        private string GetCsvDataRowSorted<T>(T csvDataObject, PropertyInfo[] propertyInfos)
        {
            IEnumerable<string> valuesSorted = propertyInfos
                .Select(x => new
                {
                    Value = x.GetValue(csvDataObject, null),
                    Attribute = (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false)
                })
                .Where(x => x.Attribute != null && x.Attribute.Export)
                .OrderBy(x => x.Attribute.Order)
                .Select(x => GetPropertyValueAsString(x.Value));
            return String.Join(",", valuesSorted);
        }

        private string GetCsvHeaderSorted(PropertyInfo[] propertyInfos)
        {
            IEnumerable<string> headersSorted = propertyInfos
                .Select(x => (CsvColumnNameAttribute)Attribute.GetCustomAttribute(x, typeof(CsvColumnNameAttribute), false))
                .Where(x => x != null && x.Export)
                .OrderBy(x => x.Order)
                .Select(x => x.Name);
            return String.Join(",", headersSorted);
        }

        private string GetPropertyValueAsString(object propertyValue)
        {
            string propertyValueString;

            if (propertyValue == null)
                propertyValueString = "";
            else if (propertyValue is DateTime)
                propertyValueString = ((DateTime)propertyValue).ToString("dd MMM yyyy");
            else if (propertyValue is int)
                propertyValueString = propertyValue.ToString();
            else if (propertyValue is float)
                propertyValueString = ((float)propertyValue).ToString("#.####"); // format as you need it
            else if (propertyValue is double)
                propertyValueString = ((double)propertyValue).ToString("#.####"); // format as you need it
            else // treat as a string
                propertyValueString = @"""" + propertyValue.ToString().Replace(@"""", @"""""") + @""""; // quotes with 2 quotes

            return propertyValueString;
        }
    }
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