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在c中动态更改列的数据类型#

Tom · 技术社区 · 4 年前

我正在c#中创建一个数据表,它将由方法a、方法B或方法c这三个方法中的任何一个调用。唯一的区别是,一列的数据类型将根据调用的方法而延迟。此数据表中的attr_value列需要根据调用更改为日期、小数或文本。我希望避免编写三种方法来创建数据表,并且我不确定if-else条件在表定义中是否合适。有人能提出一个解决这个问题的好方法吗。

public class AttributeValueInsertDate : EntityBase
    {
        public static object ResolveRequest(AttributeValueList attributeValueList)
        {
            return new
            {
                dateValuesTVP = AttributeValue.CreateAttributeValueDataTable(attributeValueList)
            };
        }
    }

 public class AttributeValueInsertDecimal : EntityBase
    {
        public static object ResolveRequest(AttributeValueList attributeValueList)
        {
            return new
            {
                decimalValuesTVP = AttributeValue.CreateAttributeValueDataTable(attributeValueList)
            };
        }

    }

 public class AttributeValueInsertText : EntityBase
    {
        public static object ResolveRequest(AttributeValueList attributeValueList)
        {
            return new
            {
                textValuesTVP = AttributeValue.CreateAttributeValueDataTable(attributeValueList)
            };
        }

    }

public class AttributeValue
{
public static DataTable CreateAttributeValueDataTable(AttributeValueList attributeValueList)
        {
            var dataTable = new DataTable();
            dataTable.Columns.Add("attr_id", typeof(Int32));
            dataTable.Columns.Add("attr_value", typeof(DateTime));
            dataTable.Columns.Add("effective_date", typeof(DateTime));
            dataTable.Columns.Add("expiration_date", typeof(DateTime));
            dataTable.Columns.Add("last_updated_user", typeof(string));
            dataTable.Columns.Add("last_updated_date_time", typeof(DateTime));

            if (attributeValueList.Count > 0)
            {
                foreach (var item in attributeValueList)
                {
                    DataRow dr = dataTable.NewRow();
                    dr[0] = item.AttributeId;
                    dr[1] = item.Value;
                    dr[2] = item.EffectiveDate;
                    dr[3] = item.ExpirationDate;
                    dr[4] = item.LastUpdatedUser;
                    dr[5] = item.LastUpdatedDate;

                    dataTable.Rows.Add(dr);
                }
            }
            return dataTable;
        }
}

0 回复 | 直到 4 年前

Tim Schmelter 4 年前

您可以使其通用,并初始化 DataColumn 具有 typeof(T) :

public static DataTable CreateAttributeValueDataTable<T>(AttributeValueList attributeValueList)
{
    var dataTable = new DataTable();
    dataTable.Columns.Add("attr_id", typeof(Int32));
    dataTable.Columns.Add("attr_value", typeof(T));
    dataTable.Columns.Add("effective_date", typeof(DateTime));
    dataTable.Columns.Add("expiration_date", typeof(DateTime));
    dataTable.Columns.Add("last_updated_user", typeof(string));
    dataTable.Columns.Add("last_updated_date_time", typeof(DateTime));

    if (attributeValueList.Count > 0)
    {
        foreach (var item in attributeValueList)
        {
            DataRow dr = dataTable.NewRow();
            dr[0] = item.AttributeId;
            dr[1] = item.Value;
            dr[2] = item.EffectiveDate;
            dr[3] = item.ExpirationDate;
            dr[4] = item.LastUpdatedUser;
            dr[5] = item.LastUpdatedDate;

            dataTable.Rows.Add(dr);
        }
    }
    return dataTable;
}

现在您可以这样称呼它:

public class AttributeValueInsertDate : EntityBase
{
    public static object ResolveRequest(AttributeValueList attributeValueList)
    {
        return new
        {
            dateValuesTVP = AttributeValue.CreateAttributeValueDataTable<DateTime>(attributeValueList)
        };
    }
}

public class AttributeValueInsertDecimal : EntityBase
{
    public static object ResolveRequest(AttributeValueList attributeValueList)
    {
        return new
        {
            decimalValuesTVP = AttributeValue.CreateAttributeValueDataTable<Decimal>(attributeValueList)
        };
    }

}

public class AttributeValueInsertText 
{
    public static object ResolveRequest(AttributeValueList attributeValueList)
    {
        return new
        {
            textValuesTVP = AttributeValue.CreateAttributeValueDataTable<string>(attributeValueList)
        };
    }

}