在调用存储过程时，产生如下错误：

Parameter 'p_R_URL': No size set for variable length data type: String.

说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。

异常详细信息: System.Exception: Parameter 'p_R_URL': No size set for variable length data type: String.

源错误:

行 67： 			catch(Exception ex)
行 68： 			{
行 69： 				throw new Exception(ex.Message);
行 70： 				//return false;
行 71： 			}

源文件: c:\inetpub\wwwroot\resource\datalay\dbresource.cs    行: 69

堆栈跟踪:

[Exception: Parameter 'p_R_URL': No size set for variable length data type: String.]
   ReSource.DataLay.DbResource.Insert(String R_TITLE, String R_USE, String R_XKML, String R_GRLB, String R_WJLB, DateTime R_ADDTIME, String R_URL, String R_PRIVATE, String R_COMMONT) in c:\inetpub\wwwroot\resource\datalay\dbresource.cs:69
   ReSource.BusLay.BusResource.Insert() in c:\inetpub\wwwroot\resource\buslay\busresource.cs:119
   ReSource.WebLay.MYRESOURCEAdd.Insert(Object sender, EventArgs e) in c:\inetpub\wwwroot\resource\weblay\tjzy\myresourceadd.aspx.cs:80
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.WebControls.LinkButton.OnClick(EventArgs e) +108
   System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +57
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +138
   System.Web.UI.Page.ProcessRequestMain() +1292

private OracleParameter CreateParameter(string name, DbType dbType, int size, ParameterDirection direction, bool nullable, byte precision, byte scale, string sourceColumn, DataRowVersion sourceVersion, object value)
        {
            OracleParameter param = this.command.CreateParameter();
            param.ParameterName = name;
            param.DbType = dbType;
            param.Size = size;
            param.Value = (value == null) ? DBNull.Value : value;
            // modify parameter type and value for special cases
            switch (dbType)
            {
                    // for Guid, change to value to byte array
                case DbType.Guid:
                    guidParameters.Add(param.ParameterName, "System.Guid");
                    param.OracleType = OracleType.Raw;
                    param.Size = 16;
                    // convert Guid value to byte array only if not null
                    if ((value is DBNull) || (value == null))
                    {
                        param.Value = Convert.DBNull;
                    }
                    else
                    {
                        param.Value = ((Guid)value).ToByteArray();
                    }
                    break;
                    //                case DbType.AnsiString:
                    //                case DbType.AnsiStringFixedLength:
                    //                case DbType.String:
                    //                case DbType.StringFixedLength:                
                    //                    // for empty string, set it to DBNull
                    //                    if ((value == null) || (!(value is DBNull)) && ((string)value).Length == 0) 
                    //                    {
                    //                        param.Value = Convert.DBNull;
                    //                    }
                    //                    break;
                default:
                    break;
            }
            param.Direction = direction;
            param.IsNullable = nullable;
            param.Precision = precision;
            param.Scale = scale;
            param.SourceColumn = sourceColumn;
            param.SourceVersion = sourceVersion;
            return param;
        }

private OracleParameter CreateParameter(string name, DbType dbType, int size, ParameterDirection direction, bool nullable, byte precision, byte scale, string sourceColumn, DataRowVersion sourceVersion, object value)
        {
            OracleParameter param = this.command.CreateParameter();
            param.ParameterName = name;
            param.DbType = dbType;
            param.Size = size;
            param.Value = (value == null) ? DBNull.Value : value;
            // modify parameter type and value for special cases
            switch (dbType)
            {
                    // for Guid, change to value to byte array
                case DbType.Guid:
                    guidParameters.Add(param.ParameterName, "System.Guid");
                    param.OracleType = OracleType.Raw;
                    param.Size = 16;
                    // convert Guid value to byte array only if not null
                    if ((value is DBNull) || (value == null))
                    {
                        param.Value = Convert.DBNull;
                    }
                    else
                    {
                        param.Value = ((Guid)value).ToByteArray();
                    }
                    break;
                    case DbType.AnsiString:
                    case DbType.AnsiStringFixedLength:
                    case DbType.String:
                    case DbType.StringFixedLength:                
                        // for empty string, set it to DBNull
                        if ((value == null) || (!(value is DBNull)) && ((string)value).Length == 0) 
                        {
                            param.Value = Convert.DBNull;
                        }
                        break;
                default:
                    break;
            }
            param.Direction = direction;
            param.IsNullable = nullable;
            param.Precision = precision;
            param.Scale = scale;
            param.SourceColumn = sourceColumn;
            param.SourceVersion = sourceVersion;
            return param;
        }

问题的到了解决。但是不知道微软的代码为什么把这个给注释掉了。

后来，上网上看到Oracle 的一个论坛上的帖子上有如下的描述：

Oracle will treat '' (empty string) as
NULL, and store as NULL anyway - better be prepared for it, and
treat it as such.