c# - 如何选择数据表中列的非重复行计数？

Question

我有一个数据表:

DataTable table = new DataTable();

DataColumn column;

column = new DataColumn();
column.DataType = Type.GetType("System.String");
column.ColumnName = "RelationshipTypeDescription";
table.Columns.Add(column);

column = new DataColumn();
column.DataType = Type.GetType("System.String");
column.ColumnName = "RelatedContactName";
table.Columns.Add(column);

我想知道列“RelationshipTypeDescription”的不同计数。

我不确定如何引用其中的列名:

int relationshipCount = table.AsEnumerable().Distinct().Count();

谁能帮我一把？

Answer 1

你可以这样做:

int relationshipCount = table
    .AsEnumerable()
    .Select(r => r.Field<string>("RelationshipTypeDescription"))
    .Distinct()
    .Count();

但您可能不需要调用 AsEnumerable:

int relationshipCount = table
    .Select(r => r.Field<string>("RelationshipTypeDescription"))  // Compiler error: "Cannot convert lambda expression to type 'string' because it is not a delegate type"
    .Distinct()
    .Count();