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>
publicCsvExport(stringcolumnSeparator =",",boolincludeColumnSeparatorDefinitionPreamble =true)
{
_columnSeparator = columnSeparator;
_includeColumnSeparatorDefinitionPreamble = includeColumnSeparatorDefinitionPreamble;
}
///<summary>
///Set a value on this column
///</summary>
publicobjectthis[stringfield]
{
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>
publicvoidAddRow()
{
_rows.Add(newDictionary<string,object>());
}
///<summary>
///Add a list of typed objects, maps object properties to CsvFields
///</summary>
publicvoidAddRows<T>(IEnumerable<T> list)
{
if(list.Any())
{
foreach(varobjinlist)
{
AddRow();
varvalues = obj.GetType().GetProperties();
foreach(varvalueinvalues)
{
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>
publicstaticstringMakeValueCsvFriendly(objectvalue,stringcolumnSeparator =",")
{
if(value ==null)return"";
if(valueisINullable&& ((INullable)value).IsNull)return"";
if(valueisDateTime)
{
if(((DateTime)value).TimeOfDay.TotalSeconds == 0)
return((DateTime)value).ToString("yyyy-MM-dd");
return((DateTime)value).ToString("yyyy-MM-dd HH:mm:ss");
}
stringoutput = 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);
}
returnoutput;
}
///<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> rowin_rows)
{
foreach(stringkin_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>
publicstringExport()
{
StringBuildersb =newStringBuilder();
foreach(stringlineinExportToLines())
{
sb.AppendLine(line);
}
returnsb.ToString();
}
///<summary>
///Exports to a file
///</summary>
publicvoidExportToFile(stringpath)
{
File.WriteAllLines(path, ExportToLines(),Encoding.UTF8);
}
///<summary>
///Exports to a file
///</summary>
publicvoidExportToFile(stringpath,Encodingencoding)
{
File.WriteAllLines(path, ExportToLines(), encoding);
}
///<summary>
///Exports as raw UTF8 bytes
///</summary>
publicbyte[] ExportToBytes()
{
vardata =Encoding.UTF8.GetBytes(Export());
returnEncoding.UTF8.GetPreamble().Concat(data).ToArray();
}
}
//具体的调用：
CsvExportmyExport =newCsvExport(); //创建对象
foreach(vardatainlist)
{
myExport.AddRow(); //添加行
foreach(varpropertyindata)
{
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
转载于:https://www.cnblogs.com/lanchong/p/7098734.html