我想对由三个不同数据表组成的数据表使用内连接，并使用 c# 作为合并数据表返回结果

Question

Table 1:Parent { Columns: ParentId , Name }

Table 2:Child { Columns: ChildId , ChildName }

Table 3:Relationship {Columns: RelationshipId , PrimaryId(ParentId) ,SecondaryId(Child Id)}

Answer 1

Try following :

           DataTable parentTable = new DataTable();
           parentTable.Columns.Add("ParentId", typeof(string));
           parentTable.Columns.Add("Name", typeof(string));

           DataTable childTable = new DataTable();
           childTable.Columns.Add("ParentId", typeof(string));
           childTable.Columns.Add("ChildNameName", typeof(string));

           DataTable relationshipTable = new DataTable();
           relationshipTable.Columns.Add("RelationshipId", typeof(string));
           relationshipTable.Columns.Add("PrimaryId", typeof(string));
           relationshipTable.Columns.Add("SecondaryId", typeof(string));

           var results = (from r in relationshipTable.AsEnumerable()
                          join p in parentTable.AsEnumerable() on r.Field<string>("PrimaryId") equals p.Field<string>("ParentId")
                          join c in childTable.AsEnumerable() on r.Field<string>("SecondaryId") equals c.Field<string>("ChildID")
                          select new { r = r, p = p, c = c })
                         .ToList();