I have a static class in which I am using dictionaries as lookup tables to map between .NET types and SQL types. Here is an example of such a dictionary:
private static readonly Dictionary<Type, string> SqlServerMap = new Dictionary<Type, string>
{
{typeof (Boolean), "bit"},
{typeof (Byte[]), "varbinary(max)"},
{typeof (Double), "float"},
{typeof (Byte), "tinyint"},
{typeof (Int16), "smallint"},
{typeof (Int32), "int"},
{typeof (Int64), "bigint"},
{typeof (Decimal), "decimal"},
{typeof (Single), "real"},
{typeof (DateTime), "datetime2(7)"},
{typeof (TimeSpan), "time"},
{typeof (String), "nvarchar(MAX)"},
{typeof (Guid), "uniqueidentifier"}
};
Then I have a public method below which passes in a .NET type and it returns the string value of the corresponding MS SQL Server type using this dictionary. However, since this is being used as a lookup table for making database queries, I think it makes sense to make it a ConcurrentDictionary. I changed it to:
private static readonly IDictionary<Type, string> SqlServerMap = new ConcurrentDictionary<Type, string>
{
{typeof (Boolean), "bit"},
{typeof (Byte[]), "varbinary(max)"},
{typeof (Double), "float"},
{typeof (Byte), "tinyint"},
{typeof (Int16), "smallint"},
{typeof (Int32), "int"},
{typeof (Int64), "bigint"},
{typeof (Decimal), "decimal"},
{typeof (Single), "real"},
{typeof (DateTime), "datetime2(7)"},
{typeof (TimeSpan), "time"},
{typeof (String), "nvarchar(MAX)"},
{typeof (Guid), "uniqueidentifier"}
};
But now it underlines everything red within the {} (i.e. all key value pairs of the ConcurrentDictionary) and the error is:
Cannot access private method 'Add' here
I don't think it's because I initialize it as private static readonly, because I just tested by making a public static version and I got the same error.
Try this
private static readonly IDictionary<Type, string> SqlServerMap =
new ConcurrentDictionary<Type, string>(
new Dictionary<Type, string>()
{
{typeof(Boolean ), "bit" },
{typeof(Byte[] ), "varbinary(max)" },
{typeof(Double ), "float" },
{typeof(Byte ), "tinyint" },
{typeof(Int16 ), "smallint" },
{typeof(Int32 ), "int" },
{typeof(Int64 ), "bigint" },
{typeof(Decimal ), "decimal" },
{typeof(Single ), "real" },
{typeof(DateTime), "datetime2(7)" },
{typeof(TimeSpan), "time" },
{typeof(String ), "nvarchar(MAX)" },
{typeof(Guid ), "uniqueidentifier"}
}
);
Updated: if you are using C#6(Roslyn 2.0 Compiler), you can use the new Dictionary Initializers.
private static readonly IDictionary<Type, string> SqlServerMap =
new ConcurrentDictionary<Type, string>
{
[typeof(Boolean )] = "bit" ,
[typeof(Byte[] )] = "varbinary(max)" ,
[typeof(Double )] = "float" ,
[typeof(Byte )] = "tinyint" ,
[typeof(Int16 )] = "smallint" ,
[typeof(Int32 )] = "int" ,
[typeof(Int64 )] = "bigint" ,
[typeof(Decimal )] = "decimal" ,
[typeof(Single )] = "real" ,
[typeof(DateTime)] = "datetime2(7)" ,
[typeof(TimeSpan)] = "time" ,
[typeof(String )] = "nvarchar(MAX)" ,
[typeof(Guid )] = "uniqueidentifier"
};
Example https://dotnetfiddle.net/9ZgjsR
The collection initializer that you're using to populate the collection only works if the collection has an Add method of an appropriate signature and accessibility. ConcurrentDictionary doesn't have a public Add method, so you won't be able to use a collection initializer with it.
You can provide some initial data by passing an IEnumerable<KeyValuePair<TKey, TValue>> as a parameter to the constructor, or you can call TryAdd (or AddOrUpdate, or any of the other methods with Add in the name) in a loop after creating the ConcurrentDictionary.
As a code example to Servy's accepted answer, in order to initialize a ConcurrentDictionary at instantiation, you can pass a type that impements IEnumerable (like a List) of KeyValuePair types to the constructor:
private static readonly IDictionary<Type, string> SqlServerMap =
new ConcurrentDictionary<Type, string>(
new List<KeyValuePair<Type, string>>
{
new KeyValuePair<Type, string>(typeof(Boolean), "bit"),
new KeyValuePair<Type, string>(typeof(Boolean), "bit"),
new KeyValuePair<Type, string>(typeof(Byte[]), "varbinary(max)"),
new KeyValuePair<Type, string>(typeof(Double), "float"),
new KeyValuePair<Type, string>(typeof(Byte), "tinyint"),
new KeyValuePair<Type, string>(typeof(Int16), "smallint"),
new KeyValuePair<Type, string>(typeof(Int32), "int"),
new KeyValuePair<Type, string>(typeof(Int64), "bigint"),
new KeyValuePair<Type, string>(typeof(Decimal), "decimal"),
new KeyValuePair<Type, string>(typeof(Single), "real"),
new KeyValuePair<Type, string>(typeof(DateTime), "datetime2(7)"),
new KeyValuePair<Type, string>(typeof(TimeSpan), "time"),
new KeyValuePair<Type, string>(typeof(String), "nvarchar(MAX)"),
new KeyValuePair<Type, string>(typeof(Guid), "uniqueidentifier")
});