7

我有 T4 模板，我想在其中生成一个 .cs 文件。

我有一个数组System.Data.DataColumn，我想在生成的代码文件中用作私有变量。

我ColumnName用作变量名、Value变量值和DataType变量数据类型。

我正在考虑在这种情况下如何初始化定义的变量：

ColumnName = "col1"
ColumnValue = "text"
DatType = System.String

我想看看输出：private System.String col1 = "text";

T4模板中的变量定义：

private <#= DataType.ToString() #> <#= ColumnName #> = "<=# ColumnValue #>"

我正在考虑编写辅助方法，它将返回常见数据类型的变量初始化字符串。就像是：

public string ValueInitializerString
        {
            get
            {

                string valueString;
                if (this.DataType == typeof(int))
                {
                    valueString = this.Value.ToString();
                }
                else if (this.DataType == typeof(string))
                {
                    valueString = string.Format("\"{0}\"", this.Value);
                }
                else if (this.DataType == typeof(DateTime))
                {
                    DateTime dateTime = (DateTime)this.Value;

                    valueString = string.Format("new DateTime({0}, {1}, {2}, {3}, {4}, {5}, {6})",
                                                              dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, dateTime.Minute, dateTime.Second, dateTime.Millisecond);
                }
                else
                {
                    throw new Exception(string.Format("Data type {0} not supported. ", this.DataType));
                }
                return valueString;
            }
        }

如果有人做了类似的事情，你能建议这是一个好主意还是可以以更方便的方式完成？也许我应该读点什么？

4

3 回答 3

3

这应该可以正常工作，尽管我会将其设为通用类。就像是

internal class DataType<T>
{
      public string Name {get;set}
      public T Value {get;set;}
      public Type Type
      {
          get { return typeof(T); }
      }

      public string VariableDefinition()
      {
          /* Construct string */
      }
}

这将更加灵活和可重用。示例用法：

<#
var dataType = new DataType<String>()
{
    Name = "col1",
    Value = "text"
};
#>

private <#= dataType.VariableDefinition() #>
于 2016-05-20T01:15:40.687 回答
1

Hope this works.

Use ExpandoObject to solve your problem. Definition of ExpandoObject as per MSDN :

It represents an object whose members can be dynamically added and removed at run time.

To set datatype and value at runtime , use Convert.ChangeType method. This creates an object of same type and value as you provide.

Reference for ExpandoObject: https://blogs.msdn.microsoft.com/csharpfaq/2009/09/30/dynamic-in-c-4-0-introducing-the-expandoobject/

Reference for Convert.ChangeType : https://msdn.microsoft.com/en-us/library/system.convert.changetype(v=vs.110).aspx

So create properties dynamically using ExpandoObject and create datatype dynamically using Convert.ChangeType.

Code : 

class Program
{
        static void Main(string[] args)
        {
        // I have used hardcoded values representing database values
        var dataTable = new DataTable();
        dataTable.Columns.Add(new DataColumn("Column1"));
        dataTable.Columns.Add(new DataColumn("Column2"));
        var row = dataTable.NewRow();
        row[0] = 1;
        row[1] = "Test Value";
        dataTable.Rows.Add(row);

        // This list below contains properties - variables , with same datatype and value
        dynamic parentList = new List<dynamic>();

        var rowOne = dataTable.Rows[0]; 
        for (int i = 0; i < dataTable.Columns.Count; i++)
        {
            dynamic child= new ExpandoObject();

            child.Property = Convert.ChangeType(row[i], row[i].GetType());
            parentList.Add(child); 
        }
    }

}
于 2016-05-23T18:07:14.230 回答
1

定义字典：

var _valueConverters = new Dictionary<Type, Func<object, string>>()
{
    { typeof(int), x => x.ToString() },
    { typeof(string), x => "\"" + x + "\"" },
    { typeof(DateTime), x => String.Format("new DateTime({0})", ((DateTime)x).Ticks) }
};

然后写一个这样的方法：

void WriteVariable<T>(string name, string value)
{
    Type typeT = typeof(T);
    if (! _valueConverters.ContainsKey(typeT))
        throw new Exception(string.Format("Data type {0} not supported. ", typeT.Name));
    Write(String.Format("{0} {1} = {2}", typeT.Name, name, _valueConverters[typeT](value)));
}

并这样称呼它：

private <#= WriteVariable<string>("col1", "text") #>;

甚至（不是真正可重用的）：

void WriteVariable<T>(string name, string value)
{
    Type typeT = typeof(T);
    if (! _valueConverters.ContainsKey(typeT))
        throw new Exception(string.Format("Data type {0} not supported. ", typeT.Name));
    Write(String.Format("private {0} {1} = {2};", typeT.Name, name, _valueConverters[typeT](value)));
}

和：

<#= WriteVariable<string>("col1", "text") #>
于 2016-05-25T21:23:40.030 回答