DbExpression VisistDbBooleanExpression(DbExpression exp)
{
DbCaseWhenExpression caseWhenExpression = SqlGenerator.ConstructReturnCSharpBooleanCaseWhenExpression(exp);
this.Visit(caseWhenExpression);
return(exp);
}
public static DbCaseWhenExpression ConstructReturnCSharpBooleanCaseWhenExpression(DbExpression exp)
{
// case when 1>0 then 1 when not (1>0) then 0 else Null end
DbCaseWhenExpression.WhenThenExpressionPair whenThenPair = new DbCaseWhenExpression.WhenThenExpressionPair(exp, DbConstantExpression.True);
DbCaseWhenExpression.WhenThenExpressionPair whenThenPair1 = new DbCaseWhenExpression.WhenThenExpressionPair(DbExpression.Not(exp), DbConstantExpression.False);
List<DbCaseWhenExpression.WhenThenExpressionPair> whenThenExps = new List<DbCaseWhenExpression.WhenThenExpressionPair>(2);
whenThenExps.Add(whenThenPair);
whenThenExps.Add(whenThenPair1);
DbCaseWhenExpression caseWhenExpression = DbExpression.CaseWhen(whenThenExps, DbConstantExpression.Null, UtilConstants.TypeOfBoolean);
return caseWhenExpression;
}
public void Process(DbMethodCallExpression exp, SqlGenerator generator)
{
List <WhenThenExpressionPair> pairs = new List <WhenThenExpressionPair>();
GetWhenThenPairs(exp.Object as DbMethodCallExpression, pairs);
pairs.Reverse();
List <WhenThenExpressionPair> whenThenPairs = pairs;
DbExpression elseExp = exp.Arguments[0];
DbCaseWhenExpression caseWhenExp = new DbCaseWhenExpression(exp.Type, whenThenPairs, elseExp);
caseWhenExp.Accept(generator);
}
public override DbExpression Visit(DbCaseWhenExpression exp)
{
this._sqlBuilder.Append("CASE");
foreach (var whenThen in exp.WhenThenPairs)
{
this._sqlBuilder.Append(" WHEN ");
whenThen.When.Accept(this);
this._sqlBuilder.Append(" THEN ");
whenThen.Then.Accept(this);
}
this._sqlBuilder.Append(" ELSE ");
exp.Else.Accept(this);
this._sqlBuilder.Append(" END");
return(exp);
}
// then 部分必须返回 C# type，所以得判断是否是诸如 a>1,a=b,in,like 等等的情况，如果是则将其构建成一个 case when
public override DbExpression Visit(DbCaseWhenExpression exp)
{
this._sqlBuilder.Append("CASE");
foreach (var whenThen in exp.WhenThenPairs)
{
// then 部分得判断是否是诸如 a>1,a=b,in,like 等等的情况，如果是则将其构建成一个 case when
this._sqlBuilder.Append(" WHEN ");
whenThen.When.Accept(this);
this._sqlBuilder.Append(" THEN ");
EnsureDbExpressionReturnCSharpBoolean(whenThen.Then).Accept(this);
}
this._sqlBuilder.Append(" ELSE ");
EnsureDbExpressionReturnCSharpBoolean(exp.Else).Accept(this);
this._sqlBuilder.Append(" END");
return(exp);
}
public void Process(DbMethodCallExpression exp, SqlGenerator generator)
{
DbExpression e = exp.Arguments.First();
DbEqualExpression equalNullExpression = DbExpression.Equal(e, DbExpression.Constant(null, UtilConstants.TypeOfString));
DbEqualExpression equalEmptyExpression = DbExpression.Equal(e, DbExpression.Constant(string.Empty));
DbOrExpression orExpression = DbExpression.Or(equalNullExpression, equalEmptyExpression);
DbCaseWhenExpression.WhenThenExpressionPair whenThenPair = new DbCaseWhenExpression.WhenThenExpressionPair(orExpression, DbConstantExpression.One);
List<DbCaseWhenExpression.WhenThenExpressionPair> whenThenExps = new List<DbCaseWhenExpression.WhenThenExpressionPair>(1);
whenThenExps.Add(whenThenPair);
DbCaseWhenExpression caseWhenExpression = DbExpression.CaseWhen(whenThenExps, DbConstantExpression.Zero, UtilConstants.TypeOfBoolean);
var eqExp = DbExpression.Equal(caseWhenExpression, DbConstantExpression.One);
eqExp.Accept(generator);
}
DbExpression ConvertDbBooleanExpression(DbExpression exp)
{
DbCaseWhenExpression caseWhenExpression = SqlGenerator.ConstructReturnCSharpBooleanCaseWhenExpression(exp);
return(caseWhenExpression);
}
public override DbExpression Visit(DbCaseWhenExpression exp)
{
return(exp);
}
static void StringConcat(DbBinaryExpression exp, SqlGenerator generator)
{
MethodInfo method = exp.Method;
List <DbExpression> operands = new List <DbExpression>();
operands.Add(exp.Right);
DbExpression left = exp.Left;
DbAddExpression e = null;
while ((e = (left as DbAddExpression)) != null && (e.Method == UtilConstants.MethodInfo_String_Concat_String_String || e.Method == UtilConstants.MethodInfo_String_Concat_Object_Object))
{
operands.Add(e.Right);
left = e.Left;
}
operands.Add(left);
DbExpression whenExp = null;
List <DbExpression> operandExps = new List <DbExpression>(operands.Count);
for (int i = operands.Count - 1; i >= 0; i--)
{
DbExpression operand = operands[i];
DbExpression opBody = operand;
if (opBody.Type != UtilConstants.TypeOfString)
{
// 需要 cast type
opBody = DbExpression.Convert(opBody, UtilConstants.TypeOfString);
}
DbExpression equalNullExp = DbExpression.Equal(opBody, UtilConstants.DbConstant_Null_String);
if (whenExp == null)
{
whenExp = equalNullExp;
}
else
{
whenExp = DbExpression.AndAlso(whenExp, equalNullExp);
}
DbExpression thenExp = DbConstantExpression.StringEmpty;
DbCaseWhenExpression.WhenThenExpressionPair whenThenPair = new DbCaseWhenExpression.WhenThenExpressionPair(equalNullExp, thenExp);
List <DbCaseWhenExpression.WhenThenExpressionPair> whenThenExps = new List <DbCaseWhenExpression.WhenThenExpressionPair>(1);
whenThenExps.Add(whenThenPair);
DbExpression elseExp = opBody;
DbCaseWhenExpression caseWhenExpression = DbExpression.CaseWhen(whenThenExps, elseExp, UtilConstants.TypeOfString);
operandExps.Add(caseWhenExpression);
}
generator._sqlBuilder.Append("CASE", " WHEN ");
whenExp.Accept(generator);
generator._sqlBuilder.Append(" THEN ");
DbConstantExpression.Null.Accept(generator);
generator._sqlBuilder.Append(" ELSE ");
generator._sqlBuilder.Append("(");
for (int i = 0; i < operandExps.Count; i++)
{
if (i > 0)
{
generator._sqlBuilder.Append(" || ");
}
operandExps[i].Accept(generator);
}
generator._sqlBuilder.Append(")");
generator._sqlBuilder.Append(" END");
}
public override DbExpression Visit(DbCaseWhenExpression exp)
{
return(exp.Accept(this._generator));
}
public abstract T Visit(DbCaseWhenExpression exp);