I'm new to Dapper, and writing a query that will pull from a provided schema and table, along with using dynamic ordering and filtering.
Dapper make dynamic parameters very simple, however, I'm not sure how to do this with tables in the order by and where clauses. Here's my method below, and I see the issues with SQL injection:
public GridData GetGridData(string schema, string table, TableDataParameters tableDataParameters)
{
using (var dbConnection = VarConnection)
{
dbConnection.Open();
if (!this.TableExists(dbConnection, schema, table))
{
throw new ItemNotFoundException($"Could not locate table {schema}.{table}.");
}
string orderyByClause = string.Join(",", tableDataParameters.SortModel.Select(s => $"[{s.ColId}] {(s.Sort.ToLower() == "asc" ? "asc" : "desc")}"));
var parameters = new DynamicParameters();
string whereClause;
if (tableDataParameters.FilterModel == null || !tableDataParameters.FilterModel.Any())
{
whereClause = "1=1";
}
else
{
whereClause = string.Join(" AND ", tableDataParameters.FilterModel.Select((fm, i) =>
{
string whereParam = $"whereParam{i}";
parameters.Add(whereParam, fm.Filter);
if (fm.Operation == "startsWith")
{
return $"[{fm.Column}] LIKE @{whereParam} + '%'";
}
throw new InvalidOperationException($"Unsupported filter operation '{fm.Operation}'");
}));
}
var query = $"SELECT COUNT(1) [total] " +
$"FROM [{schema}].[{table}] " +
$"WHERE {whereClause} " +
$"SELECT * " +
$"FROM [{schema}].[{table}] " +
$"WHERE {whereClause} " +
$"ORDER BY {orderyByClause} " +
$"OFFSET {tableDataParameters.StartIndex.Value} ROWS " +
$"FETCH NEXT {tableDataParameters.StopIndex.Value - tableDataParameters.StartIndex.Value} ROWS ONLY";
int total = 0;
using (var reader = dbConnection.ExecuteReader(query, parameters))
{
// First batch, it's the count
if (reader.Read())
{
total = reader.GetInt32(0);
}
var gridColumns = new List<GridColumn>();
var gridRows = new List<string[]>();
if (reader.NextResult() && reader.Read())
{
for (int i = 0; i < reader.FieldCount; i++)
{
string key = reader.GetName(i);
gridColumns.Add(new GridColumn(key, key, null, ""));
}
var items = new object[reader.FieldCount];
reader.GetValues(items);
gridRows.Add(items.Select(i => i.ToString()).ToArray());
}
while (reader.Read())
{
var items = new object[reader.FieldCount];
reader.GetValues(items);
gridRows.Add(items.Select(i => i.ToString()).ToArray());
}
return new GridData(tableDataParameters.StartIndex.Value, tableDataParameters.StopIndex.Value, total, gridRows.Count(), gridColumns.ToArray(), gridRows.ToArray());
}
}
}
Should I use something like DbCommandBuilder.QuoteIdentifier, https://msdn.microsoft.com/en-us/library/system.data.common.dbcommandbuilder.quoteidentifier(v=vs.110).aspx in this case? That doesn't seem like it would help so much here.
Thanks!
Dynamic parameters is an oxymoron! Dapper makes parameters easy, but you can't paramaterize table and column names. This is a restriction of SQL, not dapper. If you really want to do this, you have to use dynamic sql and string methods, and you're on your own as regards SQL injection.
You will be happier and live longer if you don't do this. It's just a bad road. You're not adding much value, and you're potentially introducing a load of problems and limitations.
It looks like you're writing an app to browse a database. Good tools already exist for this!