代码生成CSV文件

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代码生成CSV文件

简介:

逗号分隔值(Comma-Separated Values,CSV,有时也称为字符分隔值,因为分隔字符也可以不是逗号),其文件以纯文本形式存储表格数据(数字和文本)。纯文本意味着该文件是一个字符序列,不含必须像二进制数字那样被解读的数据。CSV文件由任意数目的记录组成,记录间以某种换行符分隔;每条记录由字段组成,字段间的分隔符是其它字符或字符串,最常见的是逗号或制表符。通常,所有记录都有完全相同的字段序列。

文件格式:

sep=,                    //标记分隔符(这里是","号)

A1,A2,A3,A4,A5            //表头

1,2,3,4,5                //以下的每一行表示一条记录

11,22,33,44,55

111,222,333,444,555

应用场景:

CSV是一种通用的、相对简单的文件格式,被用户、商业和科学广泛应用。最广泛的应用是在程序之间转移表格数据,而这些程序本身是在不兼容的格式上进行操作的(往往是私有的和/或无规范的格式)。因为大量程序都支持某种CSV变体,至少是作为一种可选择的输入/输出格式。常用于数据的导入与导出。

文件规则:

1、开头是不留空,以行为单位

2、可含或不含列名,含列名则居文件第一行

3、一行数据不跨行,无空行

4、以半角逗号(即,)作分隔符,列为空也要表达其存在

5、列内容如存在半角引号(即"),替换成半角双引号("")转义,即用半角引号(即"")将该字段值包含起来

6、文件读写时引号,逗号操作规则互逆

7、内码格式不限,可为 ASCII、Unicode 或者其他

8、不支持特殊字符

C# CVS文件导出类:

publicclassCsvExport

{

///<summary>

/// To keep the ordered list of column names

///</summary>

List<string> _fields = newList<string>();

///<summary>

/// The list of rows

///</summary>

List<Dictionary<string, object>> _rows = newList<Dictionary<string, object>>();

///<summary>

/// The current row

///</summary>

Dictionary<string, object> _currentRow { get { return _rows[_rows.Count - 1]; } }

///<summary>

/// The string used to separate columns in the output

///</summary>

privatereadonlystring _columnSeparator;

///<summary>

/// Whether to include the preamble that declares which column separator is used in the output

///</summary>

privatereadonlybool _includeColumnSeparatorDefinitionPreamble;

///<summary>

/// Initializes a new instance of the <see cref="Jitbit.Utils.CsvExport"/> class.

///</summary>

///<param name="columnSeparator">

/// The string used to separate columns in the output.

/// By default this is a comma so that the generated output is a CSV file.

///</param>

///<param name="includeColumnSeparatorDefinitionPreamble">

/// Whether to include the preamble that declares which column separator is used in the output.

/// By default this is <c>true</c> so that Excel can open the generated CSV

/// without asking the user to specify the delimiter used in the file.

///</param>

public CsvExport(string columnSeparator = ",", bool includeColumnSeparatorDefinitionPreamble = true)

{

_columnSeparator = columnSeparator;

_includeColumnSeparatorDefinitionPreamble = includeColumnSeparatorDefinitionPreamble;

}

///<summary>

/// Set a value on this column

///</summary>

publicobjectthis[string field]

{

set

{

// Keep track of the field names, because the dictionary loses the ordering

if (!_fields.Contains(field)) _fields.Add(field);

_currentRow[field] = value;

}

}

///<summary>

/// Call this before setting any fields on a row

///</summary>

publicvoid AddRow()

{

_rows.Add(newDictionary<string, object>());

}

///<summary>

/// Add a list of typed objects, maps object properties to CsvFields

///</summary>

publicvoid AddRows<T>(IEnumerable<T> list)

{

if (list.Any())

{

foreach (var obj in list)

{

AddRow();

var values = obj.GetType().GetProperties();

foreach (var value in values)

{

this[value.Name] = value.GetValue(obj, null);

}

}

}

}

///<summary>

/// Converts a value to how it should output in a csv file

/// If it has a comma, it needs surrounding with double quotes

/// Eg Sydney, Australia -> "Sydney, Australia"

/// Also if it contains any double quotes ("), then they need to be replaced with quad quotes[sic] ("")

/// Eg "Dangerous Dan" McGrew -> """Dangerous Dan"" McGrew"

///</summary>

///<param name="columnSeparator">

/// The string used to separate columns in the output.

/// By default this is a comma so that the generated output is a CSV document.

///</param>

publicstaticstring MakeValueCsvFriendly(object value, string columnSeparator = ",")

{

if (value == null) return"";

if (value isINullable && ((INullable)value).IsNull) return"";

if (value isDateTime)

{

if (((DateTime)value).TimeOfDay.TotalSeconds == 0)

return ((DateTime)value).ToString("yyyy-MM-dd");

return ((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss");

}

string output = value.ToString().Trim();

if (output.Contains(columnSeparator) || output.Contains("\"") || output.Contains("\n") || output.Contains("\r"))

output = '"' + output.Replace("\"", "\"\"") + '"';

if (output.Length > 30000) //cropping value for stupid Excel

{

if (output.EndsWith("\""))

{

output = output.Substring(0, 30000);

if (output.EndsWith("\"") && !output.EndsWith("\"\"")) //rare situation when cropped line ends with a '"'

output += "\""; //add another '"' to escape it

output += "\"";

}

else

output = output.Substring(0, 30000);

}

return output;

}

///<summary>

/// Outputs all rows as a CSV, returning one string at a time

///</summary>

privateIEnumerable<string> ExportToLines()

{

if (_includeColumnSeparatorDefinitionPreamble) yieldreturn"sep=" + _columnSeparator;

// The header

yieldreturnstring.Join(_columnSeparator, _fields);

// The rows

foreach (Dictionary<string, object> row in _rows)

{

foreach (string k in _fields.Where(f => !row.ContainsKey(f)))

{

row[k] = null;

}

yieldreturnstring.Join(_columnSeparator, _fields.Select(field => MakeValueCsvFriendly(row[field], _columnSeparator)));

}

}

///<summary>

/// Output all rows as a CSV returning a string

///</summary>

publicstring Export()

{

StringBuilder sb = newStringBuilder();

foreach (string line in ExportToLines())

{

sb.AppendLine(line);

}

return sb.ToString();

}

///<summary>

/// Exports to a file

///</summary>

publicvoid ExportToFile(string path)

{

File.WriteAllLines(path, ExportToLines(), Encoding.UTF8);

}

///<summary>

/// Exports to a file

///</summary>

publicvoid ExportToFile(string path, Encoding encoding)

{

File.WriteAllLines(path, ExportToLines(), encoding);

}

///<summary>

/// Exports as raw UTF8 bytes

///</summary>

publicbyte[] ExportToBytes()

{

var data = Encoding.UTF8.GetBytes(Export());

returnEncoding.UTF8.GetPreamble().Concat(data).ToArray();

}

}

//具体的调用:

CsvExport myExport = newCsvExport(); //创建对象

foreach (var data in list)

{

myExport.AddRow(); //添加行

foreach (var property in data)

{

myExport[property.Name] = property.Value; //设置列头和每一行对应的数据

}

}

myExport.ExportToFile(filePath, Encoding.Default); //按照编码导出csv文件


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