[C#]使用 泛型產生物件Update SQL (Update SQL generated objects using generics)

問題

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使用 泛型產生物件Update SQL



解決方法

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internal string GetUpdateString<T>(T obj) where T : class
{
    PropertyInfo[] srcFields = obj.GetType().GetProperties(
        BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty);

    List<string> columnString = new List<string>();
    foreach (var property in srcFields)
    {
        if (((DescriptionAttribute)((TypeDescriptor.GetProperties(this)[property.Name].Attributes)[typeof(DescriptionAttribute)])).Description == "")
        {
            if (property.GetValue(obj, null) != null)
            {
                if (property.PropertyType == typeof(decimal) ||
                    property.PropertyType == typeof(double) ||
                    property.PropertyType == typeof(int))
                {
                    columnString.Add(_getFieldName(property.Name)+ "=" + property.GetValue(obj, null).ToString());
                }
                else if (property.PropertyType == typeof(string))
                    columnString.Add(_getFieldName(property.Name)+"='" + property.GetValue(obj, null).ToString() + "'");
            }
            else
                columnString.Add(_getFieldName(property.Name) + "=" + "null");
        }

    }
    if (columnString.Count > 0)
    {
        string sql = string.Format(@"
  UPDATE  {0}
  SET {1}
  ", srcFields[0].DeclaringType.Name, string.Join(",", columnString.ToArray()));
        return sql;
    }
    else
        throw new ArgumentNullException(string.Format("發生錯誤於：{0} 物件未實體化", this.GetType().Name));
}