Linq 杂谈（之）IEnumerable<T> 转换 DataTable

Sample I:

I created a public method called LINQToDataTable as following:

public DataTable LINQToDataTable<T>(IEnumerable<T> varlist)
{
     DataTable dtReturn = new DataTable();

     // column names 
     PropertyInfo[] oProps = null;

     if (varlist == null) return dtReturn;

     foreach (T rec in varlist)
     {
          // Use reflection to get property names, to create table, Only first time, others 
          will follow 
          if (oProps == null)
          {
               oProps = ((Type)rec.GetType()).GetProperties();
               foreach (PropertyInfo pi in oProps)
               {
                    Type colType = pi.PropertyType;

                    if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition()      
                    ==typeof(Nullable<>)))
                     {
                         colType = colType.GetGenericArguments()[0];
                     }

                    dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
               }
          }

          DataRow dr = dtReturn.NewRow();

          foreach (PropertyInfo pi in oProps)
          {
               dr[pi.Name] = pi.GetValue(rec, null) == null ?DBNull.Value :pi.GetValue
               (rec,null);
          }

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

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Example: To use this method, just use the following code sample:

---------------------------------------------------------------

var vrCountry = from country in objEmpDataContext.CountryMaster
                        select new {country.CountryID,country.CountryName};

DataTable dt = LINQToDataTable(vrCountry);

Sample II

Here is my second method:

public DataTable ToDataTable(System.Data.Linq.DataContext ctx, object query)
{
     if (query == null)
     {
          throw new ArgumentNullException("query");
     }
     
     IDbCommand cmd = ctx.GetCommand(query as IQueryable);
     SqlDataAdapter adapter = new SqlDataAdapter();
     adapter.SelectCommand = (SqlCommand)cmd;
     DataTable dt = new DataTable("sd");

     try
     {
          cmd.Connection.Open();
          adapter.FillSchema(dt, SchemaType.Source); 
          adapter.Fill(dt);
     }
     finally
     {
          cmd.Connection.Close();
     }
     return dt;
}

---------------------------------------------------------------

Example: To use this method, just use the following code sample:

---------------------------------------------------------------

var vrCountry = from country in objEmpDataContext.CountryMaster
                        select new {country.CountryID,country.CountryName};

DataTable dt = LINQToDataTable(objEmpDataContext,vrCountry);