如何修复“源不包含 DataRows"? [英] How to fix "The source contains no DataRows"?

问题描述

在这里我想从两个数据表中找到匹配的记录.代码是

Here i want to find the Matched Records From Two data tables. the code is

public DataTable textfiltering(DataTable dtfff, DataTable dtff)
{
   DataTable ds = (DataTable)Session["maintxt"];
   DataTable dts = (DataTable)Session["sectxt"];
   dtfff = ds;
   dtff = dts;     

   DataTable dtMerged = (from a in dtfff.AsEnumerable()
                          join b in dtff.AsEnumerable()
                          on a["contacts"].ToString() equals b["contacts"].ToString()
                          into g                                 
                          where g.Count()>0                             
                          select a).CopyToDataTable();
           return dtMerged;    

}

当数据表不包含匹配记录时，它给出源不包含数据行"...如何纠正它..请给出您的建议

it gives "The source contains no DataRows" when Data tables does not contain Matched Records... How to rectify it..pls give your suggistions

推荐答案

两种方式:

1. 在调用 CopyToDataTable
之前检查它是否包含带有 Enumerable.Any 的行
2. 使用 dtfff.Clone 创建一个与源表具有相同架构的空数据表，并使用循环从 LINQ 查询中填充它.

1. either check if it contains rows with Enumerable.Any before you call CopyToDataTable
2. use dtfff.Clone to create an empty DataTable with the same schema as the source table and use a loop to fill it from the LINQ query.

第一种方法:

var rows = from a in dtfff.AsEnumerable()
           join b in dtff.AsEnumerable()
           on a["contacts"].ToString() equals b["contacts"].ToString()
           into g
           where g.Count() > 0
           select a;
DataTable merged;
if (rows.Any())
   merged = rows.CopyToDataTable();
else
    merged = dtfff.Clone();
return merged;

第二种方法:

DataTable merged = dtfff.Clone();
foreach (DataRow sourceRow in rows)
{
   merged.ImportRow(sourceRow);  // or add all fields manually
}
return merged;

我更喜欢第二种方法，因为它只需要执行一次查询.

I prefer the second approach since it only needs to execute the query once.

这篇关于如何修复“源不包含 DataRows"?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！