System.Data.Common.ADP.IsNull C# (CSharp) Méthode

        static internal bool IsNull(object value)
        {
            if ((null == value) || (DBNull.Value == value))
            {
                return true;
            }
            INullable nullable = (value as INullable);
            return ((null != nullable) && nullable.IsNull);
        }

        private IDbCommand BuildUpdateCommand(DataTableMapping mappings, DataRow dataRow)
        {
            if (ADP.IsEmpty(this.quotedBaseTableName))
            {
                return(null);
            }
            IDbCommand cmd = BuildNewCommand(this.updateCommand);

            // count the columns for the @p, key count, ?
            int pcount      = 1; // @p1, @p2, ...
            int columnCount = 0;
            int valueCount  = 0;
            int setCount    = 0;

            StringBuilder builder = new StringBuilder();

            builder.Append("UPDATE ");
            builder.Append(QuotedBaseTableName);
            builder.Append(" SET ");

            // search for the columns in that base table, to build the set clause
            int length = this.dbSchemaRows.Length;

            for (int i = 0; i < length; ++i)
            {
                DBSchemaRow row = this.dbSchemaRows[i];
                if ((null == row) || (0 == row.BaseColumnName.Length) || ExcludeFromUpdateSet(row))
                {
                    continue;
                }
                columnCount++;

                object value        = null;
                string sourceColumn = this.sourceColumnNames[i];  // MDAC 60079
                if ((null != mappings) && (null != dataRow))
                {
                    value = GetParameterUpdateValue(sourceColumn, mappings, dataRow, row.IsReadOnly); // MDAC 61424
                    if (null == value)                                                                // unspecified values are skipped
                    {
                        if (row.IsReadOnly)                                                           // MDAC 68339
                        {
                            columnCount--;
                        }
                        continue;
                    }
                }
                if (0 < valueCount)
                {
                    builder.Append(" , ");
                }

                builder.Append(QuotedColumn(row.BaseColumnName));
                AppendParameterText(builder, pcount);

                IDataParameter p = GetNextParameter(cmd, valueCount);
                p.ParameterName = "@p" + pcount.ToString();
                p.Direction     = ParameterDirection.Input;
                p.SourceColumn  = sourceColumn;
                p.SourceVersion = DataRowVersion.Current;
                p.Value         = value;

                if (p is OleDbParameter)
                {
                    ApplyParameterInfo((OleDbParameter)p, pcount, row);
                }
                else if (p is SqlParameter)
                {
                    ApplyParameterInfo((SqlParameter)p, pcount, row);
                }
                else if (p is OdbcParameter)
                {
                    ApplyParameterInfo((OdbcParameter)p, pcount, row);
                }
                if (!cmd.Parameters.Contains(p))
                {
                    cmd.Parameters.Add(p);
                }
                pcount++;
                valueCount++;
            }
            setCount = valueCount;
            builder.Append(" WHERE ( ");

            // search the columns again to build the where clause with optimistic concurrency
            string andclause = "";
            int    whereCount = 0;
            string nullWhereParameter = null, nullWhereSourceColumn = null;

            for (int i = 0; i < length; ++i)
            {
                DBSchemaRow row = this.dbSchemaRows[i];

                if ((null == row) || (0 == row.BaseColumnName.Length) || !IncludeForUpdateWhereClause(row))
                {
                    continue;
                }
                builder.Append(andclause);
                andclause = CommandBuilder.AndClause;

                object value        = null;
                string sourceColumn = this.sourceColumnNames[i]; // MDAC 60079
                if ((null != mappings) && (null != dataRow))
                {
                    value = GetParameterValue(sourceColumn, mappings, dataRow, DataRowVersion.Original);
                }

                bool   pkey = IsPKey(row);
                string backendColumnName = QuotedColumn(row.BaseColumnName);
                if (pkey)
                {
                    if (Convert.IsDBNull(value))
                    {
                        builder.Append(String.Format(WhereClausepn, backendColumnName));
                    }
                    else if (this.namedParameters)
                    {
                        builder.Append(String.Format(WhereClause1p, backendColumnName, pcount));
                    }
                    else
                    {
                        builder.Append(String.Format(WhereClause2p, backendColumnName));
                    }
                }
                else if (this.namedParameters)
                {
                    builder.Append(String.Format(WhereClause1, backendColumnName, pcount, 1 + pcount));
                }
                else
                {
                    builder.Append(String.Format(WhereClause2, backendColumnName));
                }

                if (!pkey || !Convert.IsDBNull(value))
                {
                    IDataParameter p = GetNextParameter(cmd, valueCount); // first parameter value
                    p.ParameterName = "@p" + pcount.ToString();
                    p.Direction     = ParameterDirection.Input;
                    if (pkey)
                    {
                        p.SourceColumn  = sourceColumn;
                        p.SourceVersion = DataRowVersion.Original;
                        p.Value         = value;
                    }
                    else
                    {
                        p.SourceColumn = null;
                        p.Value        = (ADP.IsNull(value)) ? 1 : 0;
                    }
                    pcount++;
                    valueCount++;

                    if (p is OleDbParameter)
                    {
                        ApplyParameterInfo((OleDbParameter)p, pcount, row);
                    }
                    else if (p is SqlParameter)
                    {
                        ApplyParameterInfo((SqlParameter)p, pcount, row);
                    }
                    else if (p is OdbcParameter)
                    {
                        ApplyParameterInfo((OdbcParameter)p, pcount, row);
                    }
                    if (!pkey)
                    {
                        p.DbType = DbType.Int32;
                    }

                    if (!cmd.Parameters.Contains(p))
                    {
                        cmd.Parameters.Add(p);
                    }
                }

                if (!pkey)
                {
                    IDataParameter p = GetNextParameter(cmd, valueCount);
                    p.ParameterName = "@p" + pcount.ToString();
                    p.Direction     = ParameterDirection.Input;
                    p.SourceColumn  = sourceColumn;
                    p.SourceVersion = DataRowVersion.Original;
                    p.Value         = value;
                    pcount++;
                    valueCount++;

                    if (p is OleDbParameter)
                    {
                        ApplyParameterInfo((OleDbParameter)p, pcount, row);
                    }
                    else if (p is SqlParameter)
                    {
                        ApplyParameterInfo((SqlParameter)p, pcount, row);
                    }
                    else if (p is OdbcParameter)
                    {
                        ApplyParameterInfo((OdbcParameter)p, pcount, row);
                    }

                    if (!cmd.Parameters.Contains(p))
                    {
                        cmd.Parameters.Add(p);
                    }
                }

                if (IncrementUpdateWhereCount(row))
                {
                    whereCount++;
                }
            }
            builder.Append(" )");
            cmd.CommandText = builder.ToString();
            RemoveExtraParameters(cmd, valueCount);

#if DEBUG
            if (AdapterSwitches.OleDbSql.TraceInfo)
            {
                ADP.DebugWriteLine(cmd.CommandText);
            }
#endif
            this.updateCommand = cmd;

            if (0 == columnCount)
            {
                throw ADP.DynamicSQLReadOnly(ADP.UpdateCommand);
            }
            if (0 == setCount)   // MDAC 60667
            {
                cmd = null;
            }
            if (0 == whereCount)
            {
                throw ADP.DynamicSQLNoKeyInfo(ADP.UpdateCommand);
            }
            if (null != nullWhereParameter)
            {
                DataColumn column = GetParameterDataColumn(nullWhereSourceColumn, mappings, dataRow);
                throw ADP.WhereClauseUnspecifiedValue(nullWhereParameter, nullWhereSourceColumn, column.ColumnName);
            }
            return(cmd);
        }