我如何可以验证是否列在DataRow对象存在吗？ [英] How can I validate if the column exist in a DataRow object?

问题描述

private int EmploymentID { get; set; }

private void MapFields(DataRow row)
{
        if(row.HasError)
          EmploymentID = Convert.ToInt32(row["EmploymentID"].ToString());
}

中的代码表明，它验证，如果DataRow对象有错误就其行，但我想，如果它曾经存在验证。有相当使用的DataRow的HasError方法的代码的方法？

The code shows that it validates if the DataRow object has error on its row but I want to validate if it ever exist. Is there an approach for the code rather using HasError method of DataRow?

感谢您的任何答案。

推荐答案

DataRow中有一个表属性，引用的，它是从哪里来的DataTable 。
DataTable中有一个列属性，它是一个 DataColumnCollection 。

DataRow has a Table property, referencing the DataTable that it came from. DataTable has a Columns property, which is a DataColumnCollection.

枚举该列表将让你确定表是否包含所需列。需要注意的是表上的所有行具有相同的列。

Enumerating this list will let you determine if the table contains the column you want. Note that ALL rows on the table have identical columns.

例如：

bool containsColumn = row.Table.Columns.Any(column => column.ColumnName == "EmploymentID");

值得指出的是，你可能会需要检查平等的DBNull ，除非你是100％肯定的EmploymentID永远不能返回null。

It's worth pointing out that you will likely need to check for equality to DBNull, unless you are 100% certain the EmploymentID can never be returned null.

此外，如果EmploymentID列的类型为整数，那么就可以避免任何需要进行类型转换，使用直接转换：

Also, if the EmploymentID column is typed as an integer, then you can avoid any need for type conversion, by using a direct cast:

EmploymentID = (int)row["EmploymentID"]; 

或可替换地，可使用的 DataRowExtensions 获取了一个非常巧妙的方法，其中完成所有的空检查您：

or alternatively, use DataRowExtensions for a much neater approach, which does all the null checking for you:

EmploymentID =  row.Field<int?>("EmploymentID"); 

如果EmploymentID不是一个可空INT，那么你就可以像合并值：

If EmploymentID isn't a nullable int, then you can coalesce the value like:

EmploymentID =  row.Field<int?>("EmploymentID") ?? 0;

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