C# 如何在数据表的每一列中获取最大字符串长度
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How to get Max String Length in every Column of a Datatable
提问by Ronnie Overby
I have a DataTable object. Every column is of type string.
我有一个 DataTable 对象。每列都是字符串类型。
Using LINQ, how can I get the maximum string length for every column?
使用 LINQ，如何获得每列的最大字符串长度？
采纳答案by Mehrdad Afshari
The maximum string length for the whole table (assuming at least one non-null value there, otherwise, Maxwill throw an exception):
整个表的最大字符串长度（假设那里至少有一个非空值，否则Max将抛出异常）：
int maxStringLength = dataTable.AsEnumerable()
.SelectMany(row => row.ItemArray.OfType<string>())
.Max(str => str.Length);
If you want maximum string length for eachcolumn, you could do (assuming at least one non-null value in each column, otherwise, Maxwill throw an exception):
如果您想要每一列的最大字符串长度，您可以这样做（假设每一列中至少有一个非空值，否则Max将引发异常）：
List<int> maximumLengthForColumns =
Enumerable.Range(0, dataTable.Columns.Count)
.Select(col => dataTable.AsEnumerable()
.Select(row => row[col]).OfType<string>()
.Max(val => val.Length)).ToList();
回答by roncansan
With c# 6, you can prevent the exception by adding val?.Length
使用 c# 6，您可以通过添加 val?.Length 来防止异常
var maximumLengthForColumns =
Enumerable.Range(0, dt.Columns.Count)
.Select(col => dt.AsEnumerable()
.Select(row => row[col]).OfType<string>()
.Max(val => val?.Length )).ToList();
