虽然没有公开的方法，但是在内部类System.Data.ProviderBase.FieldNameLookup中确实存在一个方法，这个方法是SqlDataReader所依赖的。

In order to access it and get native performance, you must use the ILGenerator to create a method at runtime. The following code will give you direct access to int IndexOf(string fieldName) in the System.Data.ProviderBase.FieldNameLookup class as well as perform the book keeping that SqlDataReader.GetOrdinal()does so that there is no side effect. The generated code mirrors the existing SqlDataReader.GetOrdinal() except that it calls FieldNameLookup.IndexOf() instead of FieldNameLookup.GetOrdinal(). The GetOrdinal() method calls to the IndexOf() function and throws an exception if -1 is returned, so we bypass that behavior.

using System;
using System.Data;
using System.Data.SqlClient;
using System.Reflection;
using System.Reflection.Emit;

public static class SqlDataReaderExtensions {

   private delegate int IndexOfDelegate(SqlDataReader reader, string name);
   private static IndexOfDelegate IndexOf;

   public static int GetColumnIndex(this SqlDataReader reader, string name) {
      return name == null ? -1 : IndexOf(reader, name);
   }

   public static bool ContainsColumn(this SqlDataReader reader, string name) {
      return name != null && IndexOf(reader, name) >= 0;
   }

   static SqlDataReaderExtensions() {
      Type typeSqlDataReader = typeof(SqlDataReader);
      Type typeSqlStatistics = typeSqlDataReader.Assembly.GetType("System.Data.SqlClient.SqlStatistics", true);
      Type typeFieldNameLookup = typeSqlDataReader.Assembly.GetType("System.Data.ProviderBase.FieldNameLookup", true);

      BindingFlags staticflags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.IgnoreCase | BindingFlags.Static;
      BindingFlags instflags = BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.IgnoreCase | BindingFlags.Instance;

      DynamicMethod dynmethod = new DynamicMethod("SqlDataReader_IndexOf", typeof(int), new Type[2]{ typeSqlDataReader, typeof(string) }, true);
      ILGenerator gen = dynmethod.GetILGenerator();
      gen.DeclareLocal(typeSqlStatistics);
      gen.DeclareLocal(typeof(int));

      // SqlStatistics statistics = (SqlStatistics) null;
      gen.Emit(OpCodes.Ldnull);
      gen.Emit(OpCodes.Stloc_0);
      // try {
      gen.BeginExceptionBlock();
      //    statistics = SqlStatistics.StartTimer(this.Statistics);
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Call, typeSqlDataReader.GetProperty("Statistics", instflags | BindingFlags.GetProperty, null, typeSqlStatistics, Type.EmptyTypes, null).GetMethod);
      gen.Emit(OpCodes.Call, typeSqlStatistics.GetMethod("StartTimer", staticflags | BindingFlags.InvokeMethod, null, new Type[] { typeSqlStatistics }, null));
      gen.Emit(OpCodes.Stloc_0); //statistics
      //    if(this._fieldNameLookup == null) {
      Label branchTarget = gen.DefineLabel();
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Ldfld, typeSqlDataReader.GetField("_fieldNameLookup", instflags | BindingFlags.GetField));
      gen.Emit(OpCodes.Brtrue_S, branchTarget);
      //       this.CheckMetaDataIsReady();
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Call, typeSqlDataReader.GetMethod("CheckMetaDataIsReady", instflags | BindingFlags.InvokeMethod, null, Type.EmptyTypes, null));
      //       this._fieldNameLookup = new FieldNameLookup((IDataRecord)this, this._defaultLCID);
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Ldfld, typeSqlDataReader.GetField("_defaultLCID", instflags | BindingFlags.GetField));
      gen.Emit(OpCodes.Newobj, typeFieldNameLookup.GetConstructor(instflags, null, new Type[] { typeof(IDataReader), typeof(int) }, null));
      gen.Emit(OpCodes.Stfld, typeSqlDataReader.GetField("_fieldNameLookup", instflags | BindingFlags.SetField));
      //    }
      gen.MarkLabel(branchTarget);
      gen.Emit(OpCodes.Ldarg_0); //this
      gen.Emit(OpCodes.Ldfld, typeSqlDataReader.GetField("_fieldNameLookup", instflags | BindingFlags.GetField));
      gen.Emit(OpCodes.Ldarg_1); //name
      gen.Emit(OpCodes.Call, typeFieldNameLookup.GetMethod("IndexOf", instflags | BindingFlags.InvokeMethod, null, new Type[] { typeof(string) }, null));
      gen.Emit(OpCodes.Stloc_1); //int output
      Label leaveProtectedRegion = gen.DefineLabel();
      gen.Emit(OpCodes.Leave_S, leaveProtectedRegion);
      // } finally {
      gen.BeginFaultBlock();
      //    SqlStatistics.StopTimer(statistics);
      gen.Emit(OpCodes.Ldloc_0); //statistics
      gen.Emit(OpCodes.Call, typeSqlStatistics.GetMethod("StopTimer", staticflags | BindingFlags.InvokeMethod, null, new Type[] { typeSqlStatistics }, null));
      // }
      gen.EndExceptionBlock();
      gen.MarkLabel(leaveProtectedRegion);
      gen.Emit(OpCodes.Ldloc_1);
      gen.Emit(OpCodes.Ret);

      IndexOf = (IndexOfDelegate)dynmethod.CreateDelegate(typeof(IndexOfDelegate));
   }

}

public static class DataRecordExtensions
{
    public static bool HasColumn(this IDataRecord dr, string columnName)
    {
        for (int i=0; i < dr.FieldCount; i++)
        {
            if (dr.GetName(i).Equals(columnName, StringComparison.InvariantCultureIgnoreCase))
                return true;
        }
        return false;
    }
}

在控制逻辑中使用异常被认为是不好的做法，并且会带来性能损失。它还会将抛出的# exceptions错误消息发送给分析器，并帮助任何人设置调试器在抛出异常时中断。

GetSchemaTable()也是许多答案中的另一个建议。这不是检查字段是否存在的首选方法，因为它不是在所有版本中都实现的(它是抽象的，并且在dotnetcore的某些版本中抛出NotSupportedException)。GetSchemaTable在性能方面也是过度消耗的，因为如果您查看源代码，它是一个相当繁重的函数。

如果您经常使用循环遍历字段，则可能会对性能造成较小的影响，您可能需要考虑缓存结果。

你也可以调用GetSchemaTable()在你的DataReader上，如果你想要列的列表，你不想得到一个异常…

我为Visual Basic用户写了这个:

Protected Function HasColumnAndValue(ByRef reader As IDataReader, ByVal columnName As String) As Boolean
    For i As Integer = 0 To reader.FieldCount - 1
        If reader.GetName(i).Equals(columnName) Then
            Return Not IsDBNull(reader(columnName))
        End If
    Next

    Return False
End Function

我认为这个更强大，用法是:

If HasColumnAndValue(reader, "ID_USER") Then
    Me.UserID = reader.GetDecimal(reader.GetOrdinal("ID_USER")).ToString()
End If

为了保持你的代码健壮和干净，使用一个扩展函数，像这样:

    Public Module Extensions

        <Extension()>
        Public Function HasColumn(r As SqlDataReader, columnName As String) As Boolean

            Return If(String.IsNullOrEmpty(columnName) OrElse r.FieldCount = 0, False, Enumerable.Range(0, r.FieldCount).Select(Function(i) r.GetName(i)).Contains(columnName, StringComparer.OrdinalIgnoreCase))

        End Function

    End Module

这对我来说很管用:

bool hasColumnName = reader.GetSchemaTable().AsEnumerable().Any(c => c["ColumnName"] == "YOUR_COLUMN_NAME");