有没有更好的方法来执行此操作:Convert.IsDBNull(row [somecolumn])检查

Question

有没有更好的方法来编写此代码..

MyObject pymt = new MyObject();
pymt.xcol1id= Convert.IsDBNull(row["col1id"]) ? 0 : (int)row["col1id"];
pymt.xcold2id= Convert.IsDBNull(row["col2id"]) ? String.Empty : (string)row["col2id"];
pymt.xcold3id = Convert.IsDBNull(row["CustNum"]) ? 0 : (decimal)row["xcold3id"];

这可以用一种更干净的方式来完成..就像通用方法一样？

Answer 1

您可以像这样制作通用扩展方法:

public static class DataRowExtensions {

   public static T GetValueOrDefault<T>(this DataRow row, string key) {
      return row.GetValueOrDefault(key, default(T));
   }

   public static T GetValueOrDefault<T>(this DataRow row, string key, T defaultValue) {
      if (row.IsNull(key)) {
         return defaultValue;
      } else {
         return (T)row[key];
      }
   }

}

用法:

MyObject pymt = new MyObject();
pymt.xcol1id = row.GetValueOrDefault<int>("col1id");
pymt.xcold2id = row.GetValueOrDefault<string>("col2id", String.Empty);
pymt.xcold3id = row.GetValueOrDefault<int>("CustNum"]);

Answer 2

如果您使用的是.NET 3.5,并且没有重新发明Microsoft已经为您编写的扩展方法,那么绝对有更简洁的方法来编写该代码.只需添加对System.Data.DataSetExtensions.dll的引用,您就可以执行此操作:

MyObject pymt = new MyObject
                {
                    xcol1id = row.Field<int?>("col1id") ?? 0,
                    xcol2id = row.Field<string>("col2id") ?? String.Empty,
                    xcol3id = row.Field<decimal?>("col3id") ?? 0M
                };

Answer 3

在这种情况下,我倾向于使用空合并运算符.此外,DBNull.ToString返回string.Empty,因此您不必在那里做任何花哨的事情.

MyObject pymt = new MyObject();
pymt.xcol1id= row["col1id"] as int? ?? 0;
pymt.xcold2id= row["col2id"].ToString();
pymt.xcold3id = row["CustNum"] as decimal? ?? 0;

Answer 4

 static ToType GenericConvert<ToType>(object value)
        {
            ToType convValue = default(ToType);

            if (!Convert.IsDBNull(value))
                convValue = (ToType)value;

            return convValue;
        }


MyObject pymt = new MyObject();
pymt.xcol1id= GenericConvert<int>(row["col1id"]);
pymt.xcold2id= GenericConvert<string>(row["col2id"]) ?? String.Empty;
pymt.xcold3id = GenericConvert<decimal>(row["CustNum"]);