DataRow.Field <T> （浮动列）引发无效的强制转换异常

Question

IDE Visual Studio 2015
**.NET"" 4.5
Platform WinForms

I have a database table with a column [UsedSize] FLOAT . When querying this table and storing the values in local variables I get an invalid cast exception; sample code:

SqlDataAdapter sda = new SqlDataAdapter(cmdText, conn);
DataTable dt = new DataTable();
sda.Fill(dt);

foreach (DataRow row in dt.Rows)
{
    InfoLibrary ir = new InfoLibrary();
    ir.LibraryID = row.Field<int>("LibraryID");
    ir.Name = row.Field<string>("Name");
    ir.UsedSize = row.Field<float>("UsedSize");
    ir.TotalSize = row.Field<float>("TotalSize");
    ir.TotalFileCount = row.Field<int>("TotalFileCount");                   
    ilList.Add(ir);
}

When stepping the execution and performing a "Quick Watch" on the faulty line I discovered that, by changing the line to row.Field("TotalSize"), the cell value type is zero. Why would this happen when, in the table definition, this is clearly and float ?

Answer 1

SQL Server浮点数应映射到.Net Double，请参见此处