C# 如何选择数据表中某一列的不同行数？
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How do I select the distinct row count of a column in a data table?
提问by RJ.
I have a data table:
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);
I want to know the DISTINCT COUNT OF COLUMN "RelationshipTypeDescription".
我想知道列的 DISTINCT 计数“RelationshipTypeDescription”。
I'm not sure how to refer to the column name in this:
我不确定如何在此引用列名：
int relationshipCount = table.AsEnumerable().Distinct().Count();
Can someone give me a hand?
有人可以帮我一把吗？
采纳答案by p.s.w.g
You can do this:
你可以这样做：
int relationshipCount = table
.AsEnumerable()
.Select(r => r.Field<string>("RelationshipTypeDescription"))
.Distinct()
.Count();
But you probably don't need to call AsEnumerable:
但你可能不需要调用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();
回答by Forest Kunecke
You can also create a new datatable containing only the distinct values of your table:
您还可以创建一个仅包含表的不同值的新数据表：
DataView view = new DataView(table);
DataTable distinctValues = view.ToTable(true, "RelationshipTypeDescription");
More info: https://stackoverflow.com/a/1199956/1822214
更多信息：https: //stackoverflow.com/a/1199956/1822214
